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MEDICAL AND VETERINARY 
ENTOMOLOGY 



THE MACMILLAN COMPANY 

NEW YORK • BOSTON • CHICAGO • DALLAS 
ATLANTA • SAN FRANCISCO 

MACMILLAN & CO., Limited 

LONDON • BOMBAY • CALCUTTA 
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THE MACMILLAN CO. OF CANADA, Ltd. 

TORONTO 



MEDICAL AND VETERINARY 
ENTOMOLOGY 



A TEXTBOOK FOR USE IN SCHOOLS AND COLLEGES 

AS WELL AS A HANDBOOK FOR THE USE OF 

PHYSICIANS, VETERINARIANS AND 

PUBLIC HEALTH OFFICIALS 



> 
BY 

WILLIAM B; HERMS 

ASSOCIATE PBOFESSOK OF PARASITOLOGY IN'THE UNIVERSITY OF CALIFORNIA, CONSULTING 

PARASITOLOGIST FOR THE CALIFORNIA STATE BOARD OF HEALTH, AND 

FORMERLY PROFESSOR OF ZOOLOGY AND PARASITOLOGY IN 

THE SAN FRANCISCO VETERINARY COLLEGE 

AUTHOR OF "MALARIA, CAUSE AND CONTROL," "A LABORATORY GUIDE TO THE 

STUDY OF PARASITOLOGY," "THE HOUSEFLY IN ITS RELATION TO THE 

PUBLIC HEALTH," "HOUSEFLY MANAGEMENT," ETC. 



THE MACMILLAN COMPANY 
1915 

All rights reserved 



^0 



Copyright, 1915, 
By THE MACMILLAN COMPANY 



Printed from type. Published November, 1915. 



J. S. Cu8hing Co. — Berwick & Smith Co. 
Norwood, Mass., U.S.A. 



4f 



Oti 



1 

NOV 18 1915 

©CI.A416426 



5 



Befcicatefc to 

MY STUDENTS IN PARASITOLOGY 



PREFACE 

Much of the matter contained in the following pages was pre- 
pared for the press more than six years ago, but owing to the rapid 
advances made in the field of parasitology, particularly concerning 
insects, the writer has withheld it until this time, when, after con- 
siderable revision and addition, it has seemed expedient to pub- 
lish the same. The manuscript has been in almost constant use for 
a period of six years in teaching classes in Parasitology, both in the 
University of California and in the San Francisco Veterinary Col- 
lege. It has been the aim to include herewith a large part of the 
writer's original work, some of which has until now remained un- 
published, as well as the published observations of many other 
investigators in this field, all of which has gone to build up the 
foundation of the new science of Medical Entomology. 

This book is not intended to be a comprehensive treatise, touch- 
ing all the investigations in the field of Medical Entomology, but 
rather an attempt to systematize the subject and to assist in securing 
for it a place among the applied biological sciences. However, a 
discussion is included of all of the more important diseases and irri- 
tations of man and of the domesticated animals in which insects and 
arachnids are concerned, either as carriers or as causative organisms. 

Owing to the immense literature on insects as relating to disease, 
much of which is widely scattered, the student in this field must 
spend considerable time in searching for the desired information, 
and what is more important, the information is not readily accessible 
to the physician, the veterinarian, the health officer and the sani- 
tarian. It is therefore to be hoped that this book will not only 
prove useful as a text, but also as a handbook for all individuals 
who are professionally interested in the health and well-being of 
man and beast, as affected by insects and arachnids. 

In the second place detailed accounts of experiments are included 
here and there, so that the investigator might employ the methods 
described in either the repetition of the work or in carrying on 
further investigations along the lines suggested. 

Although many special papers have been consulted in the prep- 
aration of this work, a bibliography is not included herewith, inas- 
much as this information is obtainable in much more complete form 
in the bibliographical works of other writers. Reference to special 



viii PREFACE 

papers is usually made iu footnote form, but where certain facts 
have long been accepted as common knowledge, reference is ordi- 
narily omitted. 

Sources from which assistance has been drawn are too numerous 
to adequately enumerate, but to all who have contributed toward 
the preparation of this work I wish to express my sincere apprecia- 
tion and thanks, but most particularly to my advanced students in 
parasitology, who have contributed much valuable data, and to my 
colleagues, Professor C. W. Woodworth, Dr. Edwin C. Van Dyke, 
Dr. W. A. Sawyer, and Mr. S. B. Freeborn, and to my wife, Lillie 
M. Herms, who have at all times given generous cooperation and 
kindly criticism. 

Unless otherwise credited the illustrations are from photographs 
and drawings made by the author and various assistants. Thanks 
are due particularly to Dr. William Colby Rucker for the use of 
flea drawings, to Professor Herbert Osborn for permission to repro- 
duce certain drawings of biting and sucking lice, to M. B. Mitzmain 
for photographs of Tabanas striatus, to Prof. J. S. Hine for photo- 
graphs of certain other Tabanids, and to Mr. W. C. Matthews, 
Scientific Illustrator, for valuable assistance in the preparation of 
many of the figures. 

W. B. H. 

Berkeley. California. 



CONTENTS 

CHAPTER I 



Introduction 



Scope and methods ; Economic considerations ; Control of insect- 
borne diseases ; Insect control; Field observations ; Popular opinion. 



CHAPTER II 
Parasites and Parasitism 



Parasitism ; Classes of parasites ; Effect of parasitism on the host ; 
Effect of parasitism on the parasite ; Origin of parasitism ; Systematic 
position of animal parasites. 

CHAPTER III 

Insect Anatomy and Classification 13 

General; Insect larvae; Importance of knowing internal anatomy; 
Digestive system ; Salivary system ; Wings ; Metamorphosis ; External 
Anatomy ; Key to classification. 

CHAPTER TV 

Insect Mouth Parts 23 

Importance of mouth parts ; Classification of mouth parts ; The Or- 
thopteron type ; Physopodan type ; Hemipteron type ; Dipteron type ; 
Hymenopteron type ; Lepidopteron type. 

CHAPTER V 

How Insects Carry and Cause Disease 33 

/ Environmental considerations; How insects carry disease; How in- 
sects cause disease ; Direct infectiou ; Indirect infection ; Internal 
parasitism; External parasitism ; Insect venoms. 

CHAPTER VI 

Cockroaches, Beetles, Thrips . . . . . . • .37 

The cockroaches ; Habits ; Life History ; Species and distribution ; 
The croton bug; Relation to disease transmission; Environmental con- 
siderations ; Control ; The Beetles ; Scavenger beetles ; Relation to 
disease ; May beetles and thorn-headed worms ; Saw-toothed grain 
beetles; Cantharidin. — Spanish fly ; The Thrips; Thrips and sneezing. 



CONTENTS 



CHAPTER VII 

PAGE 

The Lice 52 

The biting lice ; Habits arid life history ; Damage done ; Species of 
Trichodectidae ; Species of Phiiopteridae; Gyropidae ; Liotheidae ; To 
control poultry lice ; The sucking lice ; Life history ; Pediculosis ; 
Species affecting man ; Species affecting domesticated animals ; Relation 
to disease ; Impetigo ; Spirochetosis ; Typhus fever ; Relation to Ento- 
parasites ; Treatment and control ; Control on animals. 

CHAPTER VIII 

Bedbugs and Cone-noses 69 

The bedbugs ; Characterization ; The common bedbug ; Habits and 
life history; Method of distribution; Relation to disease; Anthrax; 
Kala-azar; Spirochetosis; Control; Fumigation; The Cone-noses ; Spe- 
cies descriptions ; Life history ; Relation to disease ; Chagas disease ; 
Control ; Treatment for bite. 

CHAPTER IX 

Mosquitoes 80 

General characteristics; Nearest allies; Life history; Internal anat- 
omy ; Characters of systematic value ; Anopheline mosquitoes ; Life 
history; Duration of adult life ; Flight; Hibernation; Breeding places ; 
Yellow fever mosquitoes; Life history; Classification of mosquitoes; 
Key to common species. 

CHAPTER X 

Mosquitoes as Disease Beakers 101 

Malaria; Mosquito transmission; Circumstantial evidence; Experi- 
mental evidence ; Description and life history of Plasmodia ; Yellow 
fever ; Stegomyia the carrier ; Time factor ; Filariasis ; Dengue ; Ver- 
ruga ; Phlebotomus flies. 

CHAPTER XI 

Mosquito Control 120 

Where mosquitoes breed; Essentials of control; Oiling methods; 
Tobacco decoctions ; Other larvaecides ; Permanent corrections ; Irriga- 
tion ; River towns and malaria; Salt marsh mosquitoes; Summer re- 
sorts; Screening; Repellents; Natural enemies; Organization of 
campaigns; Cost; When to begin work and when to close; Educational 
factor; Legislation; Economic considerations; Malaria reduction ; Yel- 
low fever reduction. 

CHAPTER XII 

Buffalo Gnats and Horseflies 143 

Buffalo gnats ; Breeding habits and life history ; The bite ; Relation 
to disease ; Pellagra; Control; Systematic; Horseflies; Breeding habits 
and life history; Bites; Relation to anthrax; Relation to surra; Con- 
trol ; Svstematic. 



CONTENTS xi 

CHAPTER XIII 

PAGE 

The Common House Fly 160 

Characteristics of the house fly ; Life history ; Influence of tempera- 
ture on life history; Breeding places; Range of flight; Longevity; 
Relation to light ; Relation to disease ; Evidence ; Typhoid fever ; 
Dysentery; Summer Diarrhea; Tuberculosis; Asiatic cholera; Yaws; 
Ophthalmia ; Eggs of parasitic worms. 

CHAPTER XI Y 

House Fly Control 184 

Introduction; Sanitary stable construction; Disposal of manures; 
Manure bins ; Garbage cans ; The sanitary privy ; Insecticides on 
manure; Hot water method ; The fly in the house ; Fly poisons ; Natural 
enemies; The community fly crusade ; Manure, stable and fly ordinances. 

CHAPTER XV 

Blood-sucking Muse ids, — Tsetse Flies, Stable Flies, Horn Flies . 207 

The tsetse flies; Habits; Structural characteristics; Life history; 
Trypanosomiasis; Sleeping sickness; Xagana; Control; Species of 
Glossina flies; Stomoxys or Stable flies; Habits; Light reactions; 
Breeding habits and life history; Longevity; Surra; Poliomyelitis; 
Control; Systematic; The horn fly; Life history; Damage done; 
Control. 



CHAPTER XVI 

Myiasis 233 

Myiasis; Dipterous larvae; Flesh flies; Texas screw worm fly; As 
affecting man; As affecting domesticated animals; Other flesh flies; 
The Congo flour maggot; Treatment for nasal myiasis; Treatment for 
animals; Preventive measures ; Anthomyiid flies ; Gastric and intestinal 
myiasis; Rat-tailed larvae; Botflies; Horse bots ; Treatment for bots ; 
Preventive measures; Ox warbles; Injury done; Economic losses; 
Treatment for warbles; Prevention; Head maggot of sheep; Treat- 
ment; Prevention; Bots in rodents; Warbles in humans; Key to the 
determination of species of fly larvae involved in myiasis. 



CHAPTER XVII 

Fleas and Louse Flies 266 

Fleas, Characteristics ; Life history ; Longevity of fleas ; Hosts and 
occurrence of species; Systematic; The commoner species; Plague; 
Plague transmission; How the flea receives and transmits plague; 
Squirrels and plague ; Flea control ; Treatment of domesticated animals 
for fleas; Rat control; Squirrel control; The Chigoe flea; Patho- 
genesis; Treatment and control; The hen flea; To control the hen flea; 
Louse flies and forest flies ; Life history; Pathogenesis; Control; Louse 
fly of the deer. 



xii CONTENTS 



CHAPTER XVIII 

PAGE 

Ticks 296 

Characteristics of Arachnida ; Characteristics of the Ixodoidea 
(Ticks); Life history; Tick mouth parts ; Feeding habits; Longevity; 
Texas cattle fever tick : Economic importance ; Life history of Texas 
fever tick; Texas fever (Piroplasmosis) ; Control of Texas fever; 
African coast fever; Rocky Mountain spotted fever; Other piroplas- 
moses ; Other common Ixodine Ticks ; The Argasine Ticks ; African 
Relapsing Fever Tick; Spirochetosis; Spinose Ear Tick; The Paja- 
roello; The Poultry Tick. 

CHAPTER XIX 

Mites '. 330 

Mite characteristics; Acariasis; Sarcoptic acariasis; Mange and 
Itch ; Remedies for M ange and Itch ; Psoroptic acariasis ; Sheep scab ; 
Life history of scab mite ; Control of scabies ; Scaly leg of poultry ; 
The follicle mites ; Harvest mites ; Louse-like mites ; Poultry mites. 

CHAPTER XX 

Venomous Insects and Arachnids, — Bees, Wasps, Spiders, 

Scorpions, etc. 351 

Insect venoms ; How introduced; The Insect sting; Bees and wasps ; 
Spiders ; The poisonous Latrodectes ; Tarantulas ; Scorpions ; The 
Pajaroello ; Other ticks ; Cone-noses ; The Vinegerone. 



APPENDIX I 
General Classification of Bacteria and Protozoa .... 375 



MEDICAL AND VETERINARY 
ENTOMOLOGY 



CHAPTER I 
INTRODUCTION 

Scope and Methods. — ■ Medical Entomology is concerned with the 
study of insects and arachnids as they relate to the transmission and 
causation of disease in man and beast, and is, therefore, a specialized 
branch of the science of Parasitology. Mosquitoes and flies have for 
centuries past been looked upon as a source of extreme annoyance to 
the human family, and students of animal husbandry and of veterinary 
medicine early recognized the importance of lice, flies and ticks as 
sources of irritation to horses, cattle, hogs, etc. But that insects and 
arachnids could be transmitters of disease was not considered seriously 
until the latter part of the last century, and that certain species could 
be the sole transmitters of specific diseases was scarcely suspected until 
the latter few years of the past and the beginning of this, the twentieth, 
century. To-day our knowledge of disease transmission by insects 
has been greatly augmented by the work of a host of individual investi- 
gators representing various departments of scientific research, such as 
Medicine, Veterinary Medicine, Bacteriology, Hygiene, Zoology and 
Entomology. 

The usual training received in any one of the departments above 
mentioned is necessarily of such a nature as to handicap any one under- 
taking health problems in which insects and arachnids are concerned. 
Therefore, to meet the ever growing demand for investigators in this 
rich field, and to satisfy the question of responsibility, the science of 
Medical Entomology has been evolved. This science shares a portion 
of the fields of Pathology, Bacteriology and Entomology ; the first, in 
that certain phases of pathology are involved ; the second, in that 
pathogenic bacteria and protozoa are concerned ; and the third, in that 
the systematic and biological relationships of the insect must be studied 
as well as the morphology of its mouth parts and digestive system. For 
example, in the study of malaria, blood corpuscles are involved, calling 
for a knowledge of both normal and diseased human blood ; an intimate 
knowledge of blood parasites is imperative; and the insect host, 

1 



2 MEDICAL AND VETERINARY ENTOMOLOGY 

^he Anopheles mosquito, must receive particular attention, as to its 
Verification, anatomy and habits. It is evident at once that a knowl- 
edge of the details of these three phases requires a specific training. 

The ultimate aim of the science of Medical Entomology is the pre- 
vention of diseases in which insects are concerned ; it is therefore an 
important adjunct to Preventive Medicine and Public Health. 

Notable instances where the control of certain diseases has depended 
upon the control of insects are, as is well known, the mosquito campaigns 
of Cuba, Panama Canal Zone and the southern United States to control 
yellow fever mainly, and in New r Jersey, California, Italy and portions of 
Africa to control malaria. Lately much attention has been paid the 
common house fly ; inasmuch as it has proved a gross carrier of certain 
enteric or intestinal diseases, campaigns of considerable proportions 
have been waged against this insect in many American cities from the 
Atlantic to the Pacific. One of the most notable examples of preventive 
work is that accomplished in San Francisco in the control of rats and 
rat fleas, thereby exterminating bubonic plague in that city and pre- 
venting its spread. 

The very close bond between Preventive Medicine and our present 
subject is at once evident, and its significance becomes more and more 
apparent as men devote themselves to this highly fertile field of investi- 
gation. 

Economic Considerations. — In this age of universal progress, 
efficiency has been made the keynote, and losses traceable to disease are 
now estimated very closely on a money basis. Even human life is given 
a definite monetary valuation. Thus the California State Board of 
Health has estimated that malaria costs the state of California §2,820,400 
annually, and this state is largely free from that disease. An attempt 
to estimate the loss due to malaria in any one of the intensely malarial 
states of the South, would produce staggering results. 

The above sum is based on the following items, viz., death of 112 
citizens, average value SI 700 ; 6000 acute cases of malaria at an average 
of $20 per year for drugs, etc. ; 6000 citizens' earning power reduced 
25 per cent by malaria (estimated average income $800) ; loss of life, 
wages and illness from other diseases given opportunity through lowered 
resistance brought about by malaria, estimating 50 deaths at $1700, and 
1000 persons ill at $100 each ; loss through sacrifice sales of farms and 
moving expenses of families leaving malarial districts, estimating 250 
families at $500; loss through depreciation in land values, estimating 
$1 per acre only on 1,000,000 acres under irrigation in parts concerned. 
Nearly or quite all of this loss could be prevented by mosquito control 
efforts. 

Reduction in value of real estate in mosquito-infested regions is quite 
unnecessary. Otherwise very desirable agricultural land is often made 
unproductive because of hordes of mosquitoes attacking man and beast ; 
and again otherwise desirable locations for summer homes are made 



INTRODUCTION 3 

uninhabitable because of the mosquito nuisance, — all of which could 
be remedied at a comparatively small cost. Real estate dealers have 
hardly begun to avail themselves of the services rendered by the study of 
these conditions. 

The expense incurred in the United States in the purchase of fly 
traps, sticky fly paper, fly poison, etc., must certainly exceed two millions 
of dollars annually, and Howard, 1 in a timely work on the economic loss 
due to insects that carry disease, estimates the cost of screening at over 
ten millions of dollars per annum. 

As affecting the animal industry equally large losses are involved. 
According to the year book of the United States Department of Agri- 
culture for 1904, the losses occasioned by Texas fever, solely transmitted 
by a tick (Margaropus annulatus), amounted to about $100,000,000. 
Ransome, in Tanners' Work for October, 1913, estimates the total loss 
produced by the ' ox warble fly ' (Hypoderma lineata), at from $55,000,000 
to $120,000,000 per year for the United States alone. 

No effort has been made to estimate the losses caused by the Texas 
screw worm and the horn fly as affecting cattle, the former producing a 
direct loss, while the latter produces largely an indirect loss due to irri- 
tation, involving loss of flesh, poor growth, reduction in milk secretion, etc. 

To poultry raisers the losses due to the fowl tick (Argas persicus) and 
the poultry mite (Dermanyssus gallinoe) must also be quite considerable. 

Control of Insect-borne Diseases. — Manifestly the control of insect- 
borne diseases depends on two general conditions. The first is the 
control of the focus, through which the insect becomes infected, the 
insect being commonly only a carrier, and not a permanent receptacle. 
In the case of certain infectious diseases in which the germ is found in the 
dejecta, i.e. feces and sputum, proper sanitary precautions are impera- 
tive ; thus properly constructed fly-tight privies prevent in large measure 
the transmission of typhoid and dysentery by flies ; the use of paper 
sputum cups (cups to be burned) and fly-tight cuspidors by victims of 
tuberculosis prevents in large measure the spread of this disease by flies. 
The rigid enforcement of " anti-spitting " laws and ordinances regulating 
the construction of privies will bring about good results. Again, proper 
regulations requiring patients known to be ill with insect-borne diseases 
to be screened against insects, prevent wholesale infection. Thus 
yellow fever quarantine is imperative in order to prevent the mosquito 
carrier (Aedes calopus) from becoming infected. If such regulations 
were applied to malaria, there would be much less of this disease. How- 
ever, in this latter case, quarantine would cause much hardship, because 
the patient may not be ill enough to require close confinement, and yet 
there is every opportunity to infect the Anopheline carrier. A further 
element of importance enters in, namely immunity, under which condi- 

1 Howard, L. O., 1909. Economic loss to the people of the United States 
through insects that carry disease. U. S. Dept. of Agr., Bureau of Entomology, 
Bull. No. 78. 



4 MEDICAL AND VETERINARY ENTOMOLOGY 

tion the infected carrier is not a menace, as in the case of yellow 
fever. 

The second factor in the control of insect-borne diseases is the 
practical extermination or control of the carrier, i.e. the insect. This 
is the safest and surest method. 

Insect Control. — In the control of disease-transmitting insects, the 
most vulnerable point in the life history is sought, and the most effec- 
tive combative methods are then applied. This involves an intimate 
knowledge of life history and habits. The more familiar we are with 
regard to these two factors, the better equipped are we to cope with the 
problems of control. 

The application of control measures may be either of a temporary 
or permanent nature. Temporary control involves the elimination of 
a nuisance for a short time, a few hours or a few days, requiring constant 
repetition ; for example, the use of formaldehyde to kill flies, or penny- 
royal or citronella to repel mosquitoes, or even oil as applied to mosquito- 
breeding pools. Permanent control, on the other hand, involves the 
elimination of breeding places, or permanent protection of the same by 
mechanical or chemical means, to prevent the deposition of insect eggs, 
for example, draining or filling up unnecessary ponds and pools of stand- 
ing water, in which mosquitoes may breed ; or placing horse manure 
and general refuse in receptacles made fly-tight in order to forestall the 
breeding of house flies. 

Permanent control measures, when feasible, will always be far less 
expensive in the end, and also very much more effective than the use of 
temporary agents in the form of insecticides, which must be applied 
over and over again, with continuous expenditure of time, labor and 
money. Standing water can often be drained off with little expense, 
whereas the repeated application of oil must eventually involve greater 
outlay and inconvenience. To illustrate, the writer at one time observed 
a small pond which was surely furnishing most of the mosquitoes for the 
neighborhood ; it was the only pond near, and was within ten feet of 
a rapidly running stream lower in elevation than the pond by at least 
eighteen inches. This pond could have been drained very easily and 
would have resulted in permanent prevention ; however, oil was being 
applied regularly. The pool was evidently of no use to any one, and 
was within the limits of a mosquito campaign. Again, the common 
house fly, a source of so much annoyance, is ordinarily combated with 
poisons, sticky fly paper and screens, when the mere removal of perhaps 
a single horse manure pile in the immediate vicinity would speedily 
give ready and permanent relief. 

Field Observations. — In the practical control of insects the obser- 
vations made in the field are indispensable to the correct interpretation 
of laboratory or clinical observations. A parasite removed from its 
normal host and brought under unnatural conditions may not function 
normally, the reproductive function is commonly disturbed, few or no 



INTRODUCTION 5 

eggs being deposited in captivity, or if so, they may not be fertile. 
Therefore, it is far preferable to carry on observations where life history 
is concerned in the field or under fairly natural conditions. 

Popular Opinion. — A crusade against disease- transmitting organ- 
isms such as insects always brings with it a storm of opposition on the 
part of not a few people, who contend that it is a breach of trust with 
Nature to proceed against any species already in existence. Few ideas 
are more firmly rooted in the mind of the average man or woman than 
that Nature has brought forth nothing that is useless in the economy 
of the human family. It must be good for something, otherwise it 
would not be in existence, and should, therefore, not be exterminated or 
even molested. True it is, that we must study Nature's ways and 
endeavor to find out what she is trying to do, then help her carry out 
her plans more quickly and more accurately. For instance, if Nature has 
provided scavengers, she is endeavoring to clean up, thus pointing out 
to man what he should do. The house fly is often spoken of as one of 
Nature's scavengers. By a careful study of the performance of this 
function by the fly, it can be determined without question that this 
insect is a very poor scavenger, and that this function is carried on better 
by other insects (e.g. certain flesh flies) which do not commonly relate 
to human food as does the house fly, if indeed this argument should 
be necessary. Certainly no one would contend that it is necessary to 
be infested with vermin as a substitute for bodily cleanliness, and surely 
no one would argue that it is a breach of trust with Nature to annihilate 
the Anopheles and Stegomyia mosquitoes, the transmitters of malaria 
and yellow fever respectively. 



CHAPTER II 
PARASITES AND PARASITISM 

Parasitism. — It is well that a distinction be made at this time 
between parasitic and predaceous insects, though the two groups will 
not remain distinct throughout all species, since the beginnings of para- 
sitism may not be readily distinguishable from the predaceous habit. 
It is evident that a parasite can only be a parasite as it lives directly at 
the expense of another organism, whether plant or animal. This defi- 
nition, however, leaves few animals, if any, out of the category, inas- 
much as the dependence of animals directly on other animals or 
plants for food is obvious. But if we restrict this meaning to position, 
living in or upon another animal or plant for purposes of food, we come 
nearer to the thought. But even here there are many organisms which 
live in or upon living animals or plants, but merely share their food 
with them without causing injury, — this we would term commensal- 
ism. Furthermore, organisms feeding in or upon dead bodies would 
not be termed parasites, except as they also attack or feed on living 
tissue, as in the case of certain flesh flies, e.g. the Texas screw worm 
fly (Chrysomyia macellaria Fabr.), which as a larva may feed on the 
flesh of either dead or living animals. Parasitism, then, involves the 
process of one organism (the parasite) feeding upon another living 
organism (the host), which host must not be destroyed before at least 
the developmental or larval period of the parasite is completed, other- 
wise the result would be disastrous to the parasite as well as to the host. 

The definition given by Braun * is " By the term Parasites is understood 
living organisms, which for the purpose of procuring food, take up their 
abode, temporarily or permanently, on or within other living organ- 
isms." This definition will exclude predaceous animals (Raubtiere), 
which capture their prey alive and usually kill it outright for purposes 
of food. 

Classes of Parasites. — Other than the two general classes, Ecto- 
parasites (external parasites) and Entoparasites (internal parasites), 
all parasites may be placed in one of the following divisions, according 
to the time spent on or within the host. Facultative parasites have the 
power of changing from one host to another of a different species, e.g. 
the cat and dog flea (Ctenocephalus canis Curtis) which may be found 

1 Braun, Max, 1905. The Animal Parasites of Man. William Wood and 
Company, New York, xviii + 453 pp. 



PARASITES AND PARASITISM 7 

on the cat, the dog, the rat and man ; the rat flea (Ceratophyllus fas- 
ciatus Bosc.) on the rat and man; the wood tick (Dermacentor varia- 
bilis Say) may be found on nearly all species of domesticated mammals 
and man. Obligatory parasites are restricted to one species of host, 
on which they are obliged to remain throughout their life history, 
e.g. the biting bird lice (Mallophaga) , which perish if removed from the 
host or if transferred to another species of animal. Intermittent para- 
sites prey on the host at intervals, coming only to feed, after which 
they leave again, e.g. female horseflies (Tabanidse) in their relation to 
horses and cattle ; or the bedbug (Cimex lectularius Linn.) in its relation 
to man. Transitory parasites pass only part of their life history at the 
expense of a given host and are, during that time, obligatory, e.g. the 
horse botflies (Gastrophilus equi Fabr.), which pass their larval or 
developmental period within the stomach of the host, the adults being 
free-living; or in other transitory parasites the remaining portion of 
the life history may be spent at the expense of an entirely different 
species of host, as is the case in tapeworms. 

Effect of Parasitism on the Host. — That an animal is parasitized 
does not necessarily involve it in death, nor even in great inconvenience, 
even though the parasite is actually living at its expense. The presence 
of a few bots in the stomach of a horse may not affect that animal in 
the least, nor would the presence of a few lice on the body of an ox. 
But with the multiplication of these parasites there will be increased 
inconvenience to both hosts. The presence of a few maggots in the fleshy 
part of a sheep's tail might cause little damage, but let these be in the 
nasal sinuses or in the brain, then the gravity of the situation becomes 
greatly augmented. Thus the effect of parasitism on the host is de- 
pendent both on the number and position of the parasite. 

Effect of Parasitism on the Parasite. — All parasites are more or less 
specialized in the direction of their habits ; e.g. fleas are laterally com- 
pressed, to effect ease of motion between hairs ; lice are horizontally 
flattened, and are provided with strong clasping organs by means of 
which they hold fast to hairs ; both of these examples are wingless and 
have sacrificed much of the ordinary means of locomotion. Ento- 
parasites are usually provided with specialized hooks, barbs, suckers, 
etc., for purposes of attachment to the alimentary canal or other organs, 
e.g. the botfly larvae, and among the Helminthes, the flukes (Trematoda), 
the tapeworms (Cestoda), etc. Perhaps, because of the ease with 
which food is secured, the sense organs are usually not strongly devel- 
oped ; the eyes may be very simple or wanting. The mouth parts differ 
in the several groups, depending on the special habits of the insect. It 
is interesting to note that the parasitic habit has resulted in the devel- 
opment of structural similarity. This is particularly apparent in the 
clasping structures of the biting and sucking lice, which belong system- 
atically to two different orders; namely, the Mallophaga and the 
Hemiptera, respectively. 



8 MEDICAL AND VETERINARY ENTOMOLOGY 

Origin of Parasitism. — ■ Modern parasites are restricted more or 
less completely to particular host animals, which necessitates the deduc- 
tion that the parasite must have developed its habit after the existence 
of the host, and in consequence parasitism must be a recently acquired 
habit on the part of a one-time free-living organism. This becomes more 
apparent by a study of the life history of the parasite ; invariably the 
earlier stages point to a primitively free-living existence. Perhaps the 
ancestors of a given group of modern parasites were attracted to the waste 
food, offal and exudations of certain animals ; the search for food having 
become simplified, they began living as messmates, or commensalists, or 
as scavengers ; the association between the two species became closer and 
eventually the line of parasitism was completed. This is also borne 
out by a study of the nearest allies of a given parasite, in which the 
gradation from the free-living animal to the parasite may be traced. 
The very close structural similarity between the free-living, wingless 
book louse, Troctes divinatoria Mull, (a member of the order Corroden- 
tia, family Psocidse) and a common hen louse, Menopon biseriatum 
Piaget (a member of the order Mallophaga), leads us to believe that the 
parasitic Mallophaga have been derived directly from the Psocidse. 
Knowing the habits of the book louse, we can easily imagine how the 
line of parasitism might eventually have become established ; i.e. from 
the eating of feathers, skins and excretions off the animal to the eat- 
ing of the same on the animal as a host is not difficult to imagine at 
least. 

Degrees of parasitism may also be illustrated by examples from the 
biting lice (Mallophaga, in which there are species having the power to 
run freely and live for a considerable length of time off the host, e.g. 
Menopon pallidum Nitzsch., the common hen louse, while other related 
species have become quite sessile, as in the extreme case of the worm- 
like louse (Menopon titan Piaget), inhabiting the gular pouch of the 
pelican. Among the fleas there are also good examples of gradation in 
habit and structure, e.g. the human flea (Pulex irritans Linn.), which 
has developed remarkable springing power and is comparatively free to 
move from place to place, while the mature female hen flea (Echidnophaga 
gallinacea Westw.) is usually quite sessile, holding fast to one point much 
like a tick. 

Systematic Position of Animal Parasites. — ■ Though parasitic animal 
organisms are found in other phyla, those affecting man and beast are 
included almost exclusively in the following : 

a. Protozoa, — unicellular animals (Fig. 1) ; e.g. Entamoeba histolytica Schaudinn, 
causing amoebic dysentery ; Plasmodium vivax Grassi and Feletti, caus- 
ing malaria ; Trypanosoma gambiense Dutton, causing African sleeping 
sickness. 

6. Nemathelminthes, — bilateral, unsegmented worms of cylindrical form (Fig. 
2) ; e.g. Trichinella spiralis Owen, causing trichinosis ; Ascaris lumbri- 
coides, roundworm of man ; Ankylostoma duodenale Dubini. a hookworm 
of man. Development is us ually direct. 



PARASITES AND PARASITISM 



9 



c. Platyhehninthes, — bilateral worms ; flattened dorsoventrally ; no anal 
opening. Usually requiring an intermediate host. 
1. Cestoda, — head or scolex with separable segments called proglottides 
(Fig. 3) ; e.g. Tcenia solium Linn., the pork tapeworm of man; Tcenia 
saginata Goeze, the beef tapeworm of man; Dipylidium caninum 
Linn., a common tapeworm of the dog. 







Fig. 1. — Types of Protozoa. A. Sarcodina, rep- 
resented by Entamoeba histolytica of Tropical 
Dysentery; B. Mastigophora, represented by 
Trypanosoma gambiense of African Sleeping 
Sickness ; C. Infusoria, represented by Balan- 
tidium coli, causative organism of a certain 
oriental dysentery (redrawn after Leuckart) ; 
D. Sporozoa, represented by (a) Coccidium 
oviforme from liver of rabbit, (b) Plasmodium 
vivax of Malaria shown in a red blood corpuscle. 
(All greatly enlarged.) 




Fig. 2. — Examples of 
parasitic round worms 
(Phylum Nemathel- 
minthes, Class Nema- 
toda). a. Round 
worm of swine (Ascaris 
suum) X .3 ; b. Tri- 
chinella spiralis (after 
Leuckart), greatly en- 
larged ; c. Hookworm 
of man (Ankylostoma 
duodenale) X 1.25. 




Fig. 3. — Examples of parasitic 
flat worms (Phylum Platyhel- 
minthes, Class Cestoda. A 
poultry tape worm (Drepani- 
dotxnia infundibuliformis 

X 1) on the left ; and a com- 
mon tape worm of cattle 
(Tcenia expansa, greatly re- 
duced) on the right. 




Fig. 4. — Example 
of parasitic flat 
worms (Phylum 
Platyhelmint h e s , 
ClassTrematoda) . 
A liver fluke of 
cattle (Distomum 
americanum) X 1. 



2. Trematoda, — alimentary canal branched; mouth in a sucker; 
Fasciola hepatica Linn., the sheep liver fluke (Fig. 4). 



e.g. 



10 



MEDICAL AND VETERINARY ENTOMOLOGY 



d. Annelida, — bilaterally symmetrical, segmented or annulated worms. 

1. Chcctopoda, — locomotor chaeta?; segmentation extending to internal 
organs, e.g. Lumbricus terrestris Linn., a common earthworm (non- 
parasitic) (Fig. 5). 




Fig. 5. — Example of seg- 
mented cylindrical worms 
(Phylum Annelida, Class 
Chsetopoda). Earth- 

worm (Lumbricus sp., X .5) 
non-parasitic, but may 
serve as an intermediary 
host for certain poultry 
tapeworms. 







Fig. 6. — Example of 
segmented cylindrical 
worms (Phylum Annel- 
ida, Class Hirudinea). 
Leech (Hirudo medi- 
cinalis) X .5. 



2. Hirudinea, — flattened ; sucker at each end of body ; arrangement of in- 
ternal organs does not correspond to external segmentation ; e.g. Hirudo 
medicinalis Linn., the medicinal leech (Fig. 6). 

Arthropoda, — segmented bod}' with jointed appendages; exoskeleton; 
bilateral symmetry ; ventral nerve-cord ; 




Fig. 



7. — Examples of the Phylum Arthropoda, Class Crustacea, a. Shrimp X 1.2 
b. Crayfish X .6 ; c. Sowbug X 2. (All three examples are non-parasitic.) 



PARASITES AND PARASITISM 



11 



1. Crustacea, — aquatic; gill respiration; two pairs of antennae; biramous 
appendages ; e.g. the shrimp, the crayfish and the sow bug. (These 
examples are non-parasitic.) (Fig. 7.) 




Fig. 8. — Example of the 
Phylum Arthropoda, Class 
Protracheata. Peripatus 
(after Folsom) X .5. 




Fig. 9. — Examples 
of the Phylum 
Arthropoda, Class 
Myriapoda. a. A 
centipede X .5 ; b. 
A millipede X .7. 



2. Protracheata, — elongate, wormlike, segmented body ; paired, unseg- 

mented appendages; one pair of antennae; tracheal respiration; 
elongate dorsal heart; e.g. Peripatus (Fig. 8) (non-parasitic). 

3. Myriapoda, — body elongate and wormlike ; each segment except first two 

and last one bearing one pair of jointed walking appendages, Centipedes, 
some of which are venomous (Fig. 9a) ; or two pairs, Millipedes (Fig. 96). 




Fig. 10. — Examples of the Class In- 
secta. a. A Reduviid (cone nose) 
X 1 ; b. A mosquito (Anopheles) X'2 ; 
c. Bed bug (Cimex) X 2.5. 

4. Insecta, — body divided into three divisions (head, thorax and abdomen) ; 
three pairs of walking appendages on thorax; two pairs of wings on 
thorax (may be reduced or absent) ; one pair of antennae ; compound 
eyes; usually three simple eyes; tracheated respiratory system; e.g. 
Conorhinus protractus Uhler (cone-nose) ; Cimex lectularius Linn, 
(bed-bug) ; Anopheles maculipennis Meig. (malaria mosquito) ; etc. 
(Fig. 10). 



12 



MEDICAL AND VETERINARY ENTOMOLOGY 



Arachnida, — head and thorax fused to form cephalothorax ; four pairs 
of walking appendages on cephalothorax (larvae may be hexapod) ; 
wingless; no antennae; eyes simple, when present; e.g. Latrodectes 







Fig. 11. — Examples of the Phylum 
Arthropoda, Class Arachnida. a. A 
spider X .5; b. A tick X 1.3; c. A 
mite X 30. 

mactans Fabr., a poisonous spider; Hadrurus hirsutus Wood, scorpion; 
Margaropus annulatus Say, the Texas fever tick ; Dermanyssus gallince 
Redi, the poultry mite ; Psoroptes communis Furst, the scab mite. 
(Fig. 11). 






CHAPTER III 



INSECT ANATOMY AND CLASSIFICATION 




Fig. 12. — A few tracheal tu- 
bules taken froni an insect. 
(Greatly enlarged.) 



The Insecta (Fig. 10) are essentially segmented animals, the prim- 
itive number of segments being probably nineteen or twenty, based on 
ontological evidence. This number is no longer evident, owing to the 
specialization of the head and posterior terminal segments. The most 
striking condition is the separation of the body into three divisions ; the 
head bearing the antennae, mouth parts and 
eyes; the thorax possessing the locomotor 
appendages, usually two pairs of wings and 
three pairs of legs; the abdomen, bearing no 
appendages except the terminal organs of 
sexual prehension in the male, or ovipositor in 
the female. The respiratory system of the 
insect consists of a complex series of tubes 
(Fig. 12) ramifying all parts of the body, 
carrying air from the outside through the 
spiracles segmentally arranged on both sides 
of the thorax and abdomen. 

Insect Larvae. — When insect larvae, para- 
sitic or accidental, are encountered in the 

body of man or beast, there may be some difficulty in classifying them 
readily, with the result that they may be incorrectly placed among the 

worms, for example, bots and warbles 
(QEstridae), or screw worms (Chrysom- 
yia) or other flesh fly larvae in cases of 
intestinal myiasis. Usually these larvae 
(Fig. 13) are short and plump, ordinarily 
possessing eleven or twelve well-marked 
segments. Furthermore, microscopic ex- 
amination will reveal a system of minute 
tubules (Fig. 12), the tracheal breathing 
system, ramifying all internal parts of 
the body, even the minutest portions 
between muscle fibers. This system is 
not present in worms. 
The larvae of Dipterous insects (flies) are commonly called "mag- 
gots " and are footless ; the larvae of Coleoptera (beetles) are called 
" grubs," and have three pairs of feeble legs ; the larvae of Lepidoptera 

13 




Fig. 13. — Insect larvae, — showing 
typical external segmentation. X 1. 



14 MEDICAL AND VETERINARY ENTOMOLOGY 

(moths and butterflies) have never less than four pairs of legs including 
prolegs and are known as "caterpillars" ; Neuropterous larvae (dobson 
flies, etc.) are not easily distinguished, but the presence of three pairs 
of legs with more than twelve body segments, including the head, will 
serve to distinguish these in at least many cases. 

Importance of Knowing Internal Anatomy. — It is important that 
the student familiarize himself with the internal anatomy of the insect, 
with special reference to the digestive system and its accessory struc- 
tures, such as the salivary glands. Two cases will point out this 
necessity : 

1st. The simplest condition in which the internal organs of insects 
are concerned in disease transmission is in the case of the house fly, in 
which pathogenic organisms are sucked up with dejecta and are passed 
out with the feces of the fly, and deposited on human food, either in 
their original virulent condition or more or less attenuated or weakened. 

2d. The more complicated condition is in the case of the Anopheles 
mosquito, which sucks up pathogenic organisms (malaria parasites) 
with the human blood, and these undergo very important and vital 
sexual changes within the body of the insect, eventually finding lodg- 
ment in the salivary glands of the same before introduction by the 
" bite " into the next human victim, — thus the insect is an essential 
intermediary host. 

Digestive System. — There are three distinct regions to the insect 
intestine (Fig. 14) ; namely, (1) the fore-gut, consisting of the mouth, 
pharynx, esophagus and proventriculus ; (2) the mid-gut, consisting 
of the stomach; and (3) the hind-gut, consisting of the ileum, colon, 



Fig. 14. — Drawing of a typical insectan alimentary tract, a. fore-gut ; b. mid-gut ; c. hind- 
gut; 1. pharynx; 2. oesophagus; 3. crop; 4. gizzard; 5. hypopharynx ; 6. mandibles; 
7. stomach ; 8. ileum ; 9. colon ; 10. rectum ; 11. anus ; 12. gastric caeca ; 13. Mal- 
pighian (excretory) tubules ; 14.. salivary gland ; 15. salivary duct. X 2. N (Adapted 
after Folsom.) 

rectum and anus. The proventriculus presents merely a widened 
portion of the esophagus in the more generalized forms and serves as a 
food receptacle. In the more specialized groups, such as the Diptera 
and Lepidoptera, the crop is expanded into a capacious pocket or pouch. 
In such forms in which the gizzard is present this organ consists of a 
highly muscular dilation provided internally with chitinous teeth for 
grinding food ; for example, the grasshopper. The stomach is a simple 



INSECT ANATOMY AND CLASSIFICATION 



15 




Fig. 15. — Salivary system (right side) of an 
insect, — a cockroach. 1. Salivary glands; 
2. Salivary duct ; 3. Common salivary duct ; 
4. Hypopharynx ; 5. Reservoir. (Adapted 
after Miall and Denny.) 



sac into which open the gastric cceca, generally few in number, which give 
rise to certain digestive fluids. At both ends of the stomach are located 
valves which direct the flow of the food. There is much variation in the 
length and degree of convolution of the hind intestine, but usually the 
three regions mentioned, namely, ileum, colon and rectum, may be 
located. Emptying into the ileum are the excretory or Malpighian 
tubules varying in number and length in the various groups of insects. 

The salivary system consists 
of a pair of salivary glands 
(Fig. 15) which may be lobed, 
situated within the head, often 
extending into the thorax. 
Usually each gland empties into 
a salivary duct, the two ducts 
joining into a common duct 
which opens into the esophagus 
or pharynx. In many species 
of insects there is present a pair 
of salivary reservoirs ; these may 
be located near the opening of 
the common duct and then pre- 
sent a compound condition, or may be situated on either side of the 
esophagus at the end of a long slender duct. 

Insect Classification. — The Medical Entomologist must be equipped 
with a good knowledge of the basic principles of classification, so as to be 
able to correctly place the insect at hand in its proper order and family at 
least, and in the case of parasitic insects should be able to run the speci- 
men to the species with the aid of a key. To determine the Order to which 
an insect belongs one need usually only know the character and structure 
of the wings when present and the type of the mouth parts. This will en- 
able the student to place at least ninety per cent of the commoner insects 
in their proper Orders. Unfortunately the parasitic forms have under- 
gone many changes such as reduction or loss of the wings and great modi- 
fication.in form, but generally the mouth parts will serve as a ready means 
for rough identification. Before passing on to a list of the Orders of 
insects, the usual basis for classification will be considered here, viz. : — 

1. Wings, — (a) presence or ab- 
sence of, (6) form, (c) structure. 

2. Mouth parts, — (a) biting 
(mandibulate), (6) sucking (haus- 
tellate) . 

3. Metamorphosis, — (a) primi- 
fcv. iA w + v, ♦• i , tive > ® sim P le (incomplete), (c) 

Fig. 16. — Hypothetical type of wing . i / i , \ 

venation. A. anal vein; C. costa ; Complex (complete). 

£■:&££! &&2?fc£££Z: Wings -The earliest systems 

after Comstock and Needham.) or insect classification were based on 




16 



MEDICAL AND VETERINARY ENTOMOLOGY 



wing characters, which together with the mouth parts offer a basis for 
the more modern arrangement also. The venation of insect wings is 
so markedly characteristic for each species that even a part of a wing is 



2. d vein 




Fig. 17. — Wing of an insectf(Tabanus) , to illustrate terminology as applied to venation 
and cells. 



often all that is necessary for determination. There are typically two 
pairs of wings present, situated on the mesothorax and metathorax, 
though in many parasitic insects, such as the bedbugs, lice, fleas, cer- 
tain louse flies, etc., the wings are 
absent. Wingless insects such as 
those mentioned should not be in- 
cluded with the Aptera, which is an 
order of primitively wingless insects. 
The parasitic wingless insects fall 
under several different orders, as 
will be seen. To avert confusion it 
is therefore probably better to dis- 
pense with the term Aptera and 
substitute the term Thysanura as 
used by a number of entomologists. 
In form the wing presents a 
more or less triangular appearance. 
Generally the fore and hind wings 
differ considerably in size ; the fore 
wing in some groups, such as the 
May flies, man} 7 butterflies and 
;ta _ moths, and the bees and^ wasps, is 
morphosis. a. young of a Thysanuran larger than the hind wing, while 
Sme* ( (SSr P Ke e a^g 6 ) ^ " ^ ™ the grasshoppers, cockroaches, 

beetles, etc., the fore wing is narrow 
and serves largely as a cover (elytron) to the hind wing, which folds 
tanlike. Again, in the dragon flies, white ants and ant lions, the fore 




INSECT ANATOMY AND CLASSIFICATION 



17 




and hind wings are nearly equal. In the flies, the hind pair of wings is 
replaced by club-shaped organs known as halteres, leaving consequently 
only one pair of wings, hence the name Diptera (two-winged). 

There is also a great variation in structure of the wings, though 
for each order a certain general condition prevails ; e.g. the Neuroptera 
have thin membra- 
nous wings, often quite 
filmy ; however, Dip- 
tera and many Hem- 
iptera have the same 
texture, but possess- 
ing fewer wing veins 
and a different vena- 
tion. The Diptera 
can, of course, be 
readily distinguished 
by the presence of 
but a single pair of 
wings. The typical 
Hemiptera have the 
front wings thickened 
at the base, while 
the apical portion is 
membranous (Hemip- 
tera-Heteroptera). 
The other two divi- 
sions of this order, 
one of which has a 
pair of entirely mem- 
branous wings (Hem- 
iptera-Homoptera), 
the other wingless 
(Hemipt era-Pa ra- 
sita), can be readily 
distinguished on the 
basis of mouth parts. 

The venation of 
the insect wing, as 
has been mentioned, is an important factor in classification on account 
of the great variety of arrangement, and the reliability of this character 
for identification of the family and species. By a careful study of the 
evidence, a fundamental type of wing venation has been constructed by 
Comstock and Needham. The figure (Fig. 16) illustrating this type 
will be useful in determining the identity of the principal veins. The 
spaces between the veins are called cells, shown in Fig. 17, which figure 
also illustrates the use of the numerical system of nomenclature. 





wingi 
molt 



simple metamorphosis. a. Young 
; b. Showing wing pads after the first 
c. Adult of the same. (Redrawn after Packard.) 



grasshopper 



18 MEDICAL AND VETERINARY ENTOMOLOGY 

Metamorphosis. — In order to attain to the size and development 
of the parent the young insect undergoes greater or less change in size, 
form and structure, which series of changes is termed metamorphosis. 
The least change is found in the Thysanura (Aptera), which are primi- 
tively wingless, and hence the newly emerged young individual is ex- 
ternally unlike the parent only in size, — this type of metamorphosis 
is termed primitive (Fig. 18). 

A greater difference is found in the young and adult grasshopper 
(Fig. 19). Other than the difference in size and sexual maturity the 
absence of wings in the young is at once apparent. In order to reach 
the winged condition, the young individual molts at intervals, and with 
each molt secures longer wings until after a definite number of molts 
the fully developed wings are present. The following stages may be 
recognized : (1) egg, (2) nymph, (3) imago (not sexually mature) and 
(4) adult or sexually mature individual. This type of metamorphosis 
is termed simple or incomplete. 

The greatest difference between the newly hatched young and the 
parent occurs in such forms as the house fly (Fig. 20), the butterfly, 



'■J , - • 


i 


1 a 


$ 


I 



Fig. 20. — Illustrating complex metamorphosis. Life history of the common housefly. 
a. egg; b. larva; c. pupa; d. adult. 

etc. In these forms the newly emerged young individual has no re- 
semblance whatever to the adult, having the appearance of a seg- 
mented worm. (Of course, the internal anatomy and certain other 
features are distinctly insectan.) The fact that the young are man- 
dibulate and the adults haustellate in Diptera and Lepidoptera offers 
much interesting ground for ecological discussion, but is out of order 
at this time. In order to attain the winged condition of the adult 



INSECT ANATOMY AND CLASSIFICATION 19 

from the wingless, wormlike condition of the young, many profound 
changes must be undergone and a new stage is entered, the pupa, or rest- 
ing stage, in which this transformation is accomplished. The newly 
emerged young insect is called the larva, and we have consequently the 
following stages to deal with : (1) egg, (2) larva, (3) pupa, (4) imago, 
(5) adult. This type is termed complex or complete metamorphosis. 

External Anatomy. — In order to familarize himself with the external 
anatomy of insects, especially with the parts upon which classification 
is mainly based, the student should study carefully some hard-bodied 
insect of a generalized nature. Such an insect need not be a parasite, 
indeed, the author prefers that a non-parasitic form be used because 
there is less specialization. The common grasshopper answers the 
purpose very well, and a careful study of Fig. 21 is recommended. 

JKeys to Classification. — The student is now prepared to better 
understand the use of a key to classify any insect at hand. The first 
thing he needs to do is to place the insect in its proper order, which may 
be done with the aid of the following key. While the use of a key in 
classification of animals may seem to be essential, the student should 
not become a slave to this very mechanical method of placing creatures 
in their proper class, order or family. 

Key to the Orders of Insects l 

A. Primitive ivingless insects; mouth parts well developed, but all except the apices 
of the mandibles and maxiliaz withdrawn into a cavity in the head; tarsi 
(feet) always one or two clawed ; body sometimes centipede-like, with 
well-developed abdominal legs, in this case tarsi two-clawed — (the 

simplest insects) APTERA 

A A. Normally winged insects, wings sometimes rudimentary or absent ; mouth 
parts not withdrawn into a cavity in the head. 

B. Mouth parts, when developed, with both mandibles and maxillce fitted 
for biting; abdomen broadly joined to thorax; tarsi never bladder- 
shaped; when mouth parts are rudimentary, if the wings are two, 
there are no halteres ; if the wings are four or absent, the body is 
. not densely clothed with scales. 

C. Posterior end of abdomen with a pair of prominent unjointed. 
forceps-like appendages ; fore wings, when present, short vein- 
less, horny or leathery — (Earwigs) . . EUPLEXOPTERA 
CC. Posterior end of abdomen usually ivithout prominent unjointed 
forceps-tike appendages; when these are present the fore 
wings are always developed, veined. 

D. Fore wings, when present, veined and membranous, parch- 
ment-like or leathery, when absent, the labium (under- 
lip) either cleft in the middle, or the mouth parts pro- 
longed into a distinct beak. 

E. Fore icings, when present, thicker than hind ivings, 
somewhat leathery or parchment-like ; hind wings 
folded several times, lengthwise, like a fan, in repose; 
when wings are absent, pro thorax large — 
(locusts, crickets, cockroaches, etc.) 

ORTHOPTERA 

1 After Kellogg (by permission) arranged by Professor H. E. Summers. 



20 



MEDICAL AND VETERINARY ENTOMOLOGY 




S 3i 



aiD 



M 



•S-S 

^ 02 
J" 



w 



INSECT ANATOMY AND CLASSIFICATION 21 

EE. Fore wings membranous, of same structure as hind 
wings; hind wings usually not folded; but oc- 
casionally folded like a fan; when wings are 
absent, pro thorax small. 
F. Antennas inconspicuous. 

G. Hind wings smaller than fore or absent; 
posterior end of abdomen ivith two or 
three many-jointed filaments — (May 

flies) EPHEMERIDA 

GG. Hind wings not smaller than fore; posterior 
end of abdomen withoxd many-jointed 
filaments — (dragon flies and damsel 

flies) ODONATA 

FF. Antennce conspicuous. 

G. Tarsi less than five-jointed; labium cleft 
in the middle. 

H. Wings always present, although some- 
times very small; hind wings 
broader than fore wings, folded in 
repose; prothorax large, nearly- 
flat on dorsal surface — (Stone 
flies) . . . PLECOPTERA 
HH. Hind wings, when present, not broader 
than fore wings, not folded in re- 
pose, prothorax small, collar-like. 
I. Tarsi four-jointed, wings when 
present equal in size — (Ter- 
mites) . . . ISOPTERA 
77. Tarsi one to three jointed. 

J. Tarsi one or two jointed 
always wingless — (bit- 
ing lice) 

MALLOPHAGA 
J J. Tarsi usually three-jointed ; 
occasionally two-jointed, 
in which case wings al- 
ways present, fore wings 
larger than hind wings — 
(Book lice, etc.) 

CORRODENTIA 
GG. Tarsi five-jointed, but with one joint some- 
times difficult to distinguish; labium 
usually entire in middle, sometimes 
slightly emarginate. 

H. Wirgs, when present, naked or 

slightly hairy; hind wings ivith or 

without folded anal space; in 

former case prothorax large and 

nearly flat on dorsal surface; in 

wingless forms mouth prolonged 

into a distinct beak. 

I. Mouth parts not prolonged into a 

distinct beak, at most slightly 

conical — (Dobsons, ant 

lions, etc.) NEUROPTERA 



MEDICAL AND VETERINARY ENTOMOLOGY 

II. Mouth parts prolonged into a dis- 
tinct beak — (Scorpion flies, 
etc.) . . MECOPTERA 
HH. Wings, when present, thickly covered 
with hairs; hind wings usually 
with folded anal space; prothorax 
small, collar-like; mouth not pro- 
longed into a beak — (Caddis 
flies) . . . TRICHOPTERA 
DD. Fore wings, when present, veinless; horny or leathery; 
when absent, labium entire, and mouth parts not pro- 
longed into a distinct beak— (Beetles) COLEOPTERA 
BB. Mouth parts, when developed, more or less fitted for sucking; sometimes 
also fitted in part (the mandibles) for biting; in this case either 
(1) base of abdomen usually strongly constricted, joined to thorax 
by a narrow peduncle, or (2) the tarsi bladder-shaped, without claws; 
when mouth is rudimentary either the wings are two and halteres 
are present, or the wings are four or none and the body (and wings 
if present) are densely clothed with scales. 

C. Prothorax free ; body (and wings if present) never densely clothed 
with scales; maxillary palpi usually absent; when present, 
tarsi bladder-shaped, without claws. 

D. Tarsi bladder-shaped, without claws ; wings four (sometimes 
absent), narrow, fringed with long hairs; maxilla? trian- 
gular, with palpi— (Thrips) . THYSANOPTERA 
DD. Tarsi not bladder-shaped, usually clawed; wings not fringed 
with long hairs ; maxilla (when mouth is developed) bristle- 
like, without palpi— (Bugs) . . . HEMIPTERA 
CC. Prothorax not free; maxillary palpi present, sometimes rudi- 
mentary and difficult to see, in which case body (and wings if 
present) densely clothed with scales; tarsi never bladder- 
shaped, usually clawed. 
D. Mandibles often rudimentary, when present bristle-like. 

E. Wings four (sometimes wanting), clothed with scales; 
body covered thickly with scales or hairs; mouth, 
when developed, a slender, sucking proboscis, closely 
coiled under head — (Moths and butterflies) 

LEPIDOPTERA 

EE. Wings two (or wanting), naked or with scattered hairs; 

hind wing in winged forms represented by halteres ; 

body either naked or with scattering hairs; mouth, 

a soft or horny beak not coiled under head. 

F. Prothorax poorly developed, scarcely visible from 

dorsalside — (Flies) .... DIPTERA 

FF. Prothorax well developed, distinctly visible from 

dorsal side; wings never present (Fleas) 

SIPHONAPTERA 

DD. Mandibles well developed, fitted for biting; wings four 

(sometimes two or none), naked or with scattered hairs — 

(Ichneumon flies, gallflies, wasps, bees and ants) 

HYMENOPTERA 




CHAPTER IV 



INSECT MOUTH PARTS 



Importance of Mouth Parts. — It is evident that an insect possessing 
mouth parts capable of penetrating the skin of the higher animals must 
be looked upon as a possible carrier of blood infection, although it may, 





Fig. 22. — Head and proboscis of the common house fly (Musca domestica) on the left; 
the stable fly (Stomoxys calcitrans) on the right. Though closely related systematically, 
the mouth parts of the two species are very- different ; both are suctorial, but the former 
cannot pierce the skin while the proboscis of the latter encloses piercing setse adapted for 
that purpose. 



in actual experience, never attack such animals. If the insect is pro- 
vided with mouth parts of the usual biting type or is non-piercing, it 
cannot relate to the transmission of infection introduced into the cir- 
culation, except through a previously inflicted open wound. 

23 



24 MEDICAL AND VETERINARY ENTOMOLOGY 

The mosquito would be harmless as far as malaria and yellow fever 
are concerned if the mouth parts were of the mandibulate or biting type. 
These insects together with certain other species such as the stable fly 
(Stomoxys calcitrans), the tsetse flies and the ticks are important be- 
cause of the power which they possess of piercing the skin of higher ani- 
mals and thus introducing pathogenic organisms into the blood. 

The actual measures of control are often dependent on a knowledge 
of the mouth parts of the insect concerned. 

Classification of Mouth Parts. — From the standpoint of Medical 
Entomology it is not serviceable to divide insects into only two general 
groups based on the mouth parts, i.e., mandibulata (biting) and haustel- 
lata (sucking). This becomes evident when it is considered that the 
house fly (Musca domestica) and the stable fly (Stomoxys calcitrans) both 
have haustellate mouth parts (Fig. 22), belong to the same family 
(Muscidse), and are, therefore, systematically closely related ; yet from 
the standpoint of disease transmission differ widely. By virtue of the 
piercing stylets enclosed within the labium, the stable fly relates to direct 
infection (inoculation), while the proboscis of the house fly, quite ineffec- 
tive as a piercing organ, relates it to indirect infection. Because of the 
deficiencies of the older systems of mouth-part classification the follow- 
ing types will be recognized. 

1 . Orthopteron type, — generalized mouth parts consisting of opposable jaws used 

in biting and chewing, as in the grasshopper. 

2. Physopodan type, — mouth parts representing an intermediate type; ap- 

proaching the biting form, but functioning as suctorial organs, as in 
the thrips. 

3. Hemipteron type, — mouth parts consisting of piercing suctorial organs, com- 

prising three or four stylets closely ensheathed within the labium, as 
in the cone-nose and bedbug. 

4. Dipteron type, — suctorial organs, piercing or non-piercing ; no special rep- 

resentative is available for the entire group of Diptera, hence the 
following subtypes must be recognized. 

a. First subtype, — mosquito ; mouth parts consisting of six piercing 

stylets, loosely ensheathed within the labium. 

b. Second subtype, — horsefly ; mouth parts consisting of six short blade- 

like structures used for piercing and cutting, all loosely ensheathed 
within the labium. 

c. Third subtype, — stable fly ; mouth parts consisting of two heavy, 

piercing stylets, closely ensheathed within the labium. 

d. Fourth subtype, — house fly ; mouth parts consisting of a muscular 

proboscis, not suited for piercing; stylets aborted. 

5. Hymenopteron type, — mouth parts consisting of suctorial, lapping organs, 

mandibles specialized for portage and combat, as in the bee, wasp and 
ant. 

6. Lepidopteron type, — mouth parts consisting of a suctorial coiled tube, as in 

the cabbage butterfly. 



INSECT MOUTH PARTS 



25 



Morphology of Mouth Parts 

The Orthopteron Type. — To illustrate this type either the grass- 
hopper or the cockroach may be used, but since the former is more easily 
obtainable and can be handled more satisfactorily, it will serve this 
purpose well. This type, the mandibulate or biting, is the generalized 
or primitive form and will serve as a basis for later comparisons and 
derivations. It is not of direct importance in relation to Medical Ento- 
mology except as 
it furnishes a basis 
for a better un- 
derstanding of the 
haustellate or 
sucking type. 

If the head of 
the grasshopper 
(Fig. 23) is viewed 
from the side and 
again from the 
front, the relative 
position of the 
parts will be bet- 
ter understood. 
Separating the 
mouth parts (Fig. 
24) of the grass- 
hopper, the fol- 
lowing structures 
will be observed. 

In front, low down on the head, hangs the labrum or upper lip, easily 
lifted as one would raise a hinged lid, the hinge line being at the lower 
part of the sclerite or plate, known as the clypeus. 

The labium functions as does the upper lip in higher animals, i.e., it 
draws the food toward the mandibles. In this the labrum is greatly 
aided by a rough structure called the epipharynx, which forms the inner 
lining of the labrum and clypeus. Because of the close association of 
these two structures they are often referred to as a double organ, the 
labrum-epipliarynx. Removing the labrum, a pair of heavy, black, 
opposable jaws, the mandibles, is exposed. These are biting structures 
par excellence. They are toothed and movable laterally, instead of ver- 
tically as in the vertebrates. Dislodging the mandibles brings into view 
the pair of maxillae, or accessory jaws. These organs are known as first 
maxilla?. They are composite structures separable into cardo, stipes, 
lacinia, galea and palpus, which should be carefully observed, inasmuch 
as they undergo great modification in the remaining types of mouth parts. 
The two supporting sclerites of the maxillse are called the cardo (basal) 





Fig. 23. — Head of a grasshopper, to illustrate the relative posi- 
tion of head structures in insects. A. side view ; B. front 
view. 1. antennas; 2. compound eye ; 3. ocelli (simple eyes) ; 
4. gena (cheek); 5. clypeus; 6. labrum; 7. palpi; 8. labium. 
(Redrawn after Folsom.) 



26 



MEDICAL AND VETERINARY ENTOMOLOGY 



and stipes (the second), while the distal lobes are called (1) the maxillary 
palpus (a jointed structure), (2) the galea (median and fleshy), (3) the 
lacinia (inner and toothed, capable of aiding in comminuting food). 







Fig. 24. — Mouth parts of a grasshopper, typical mandibulate structures, Orthopteron 
type. a. labrum ; b. mandibles ; c. maxilla, consisting of (1) cardo, (2) stipes, 
(3) palpus, (4) lacina, (5) galea; d. labium, consisting of (1) submentum, (2) mentum, 
(3) palpus, (4) ligula ; e. hypopharynx or tongue. 

Underneath the maxillae and forming the floor of the mouth lies the 
lower lip or labium, a double structure frequently called the second 
maxilla. On the same plan as the maxillse, the labium consists of a 
basal sclerite, the submentum, followed by the mentum, upon which rest 



INSECT MOUTH PARTS 



27 




the labial palpi (a pair of outer jointed 
structures to the right and left), and the 
ligula (a pair of strap-like plates which 
together correspond to the upper lip) . The 
labium is also subject to much modification 
in insects. 

The fleshy organ still remaining in 
the mouth cavity after the parts just de- 
scribed have been removed is the tongue 
or hypopharynx, an organ of taste, func- 
tionally comparable to the tongue of verte- 
brates. 

The mandibles are most useful landmarks, 
since they are almost universally present in 
insects, though in various degrees of devel- 
opment from the strong mandibles of cer- 
tain beetles (Lucanidse) to the vestigial 
structures in certain Lepidoptera. In the 

u x xi i xi j • £ Fig. 25. — Head and mouth parts 

Hymenoptera, even though the order is ol of thrips, mandibuiate in struc- 
the haustellate type, the mandibles are never- 
theless important structures, serving, for ex- 
ample, in the honeybee as wax implements 
and organs of defense, and in ants as organs 
of portage and combat. In Hemiptera 
and Diptera the mandibles are modified 
into piercing organs. The maxillae are subjected to great modification. 
Physopodan Type. — Though like the first type, unimportant in its 

f relation to disease trans- 

mission, this type, the 
Physopodan (Fig. 25), is 
distinctly important phylo- 
genetically as a connecting 
link between the biting 
and piercing-sucking mouth 
parts. It is in the very 
minute thrips (Physopoda) 
that we find a transitional 
type of mouth parts, biting 
in general structure but 
sucking in function. The 
parts are all more or less 
readily traceable to the 
generalized Orthopteron 
type, but have become 
considerably elongated for 



ture but crudely suctorial in 
function. Physopodan type. 
Front view of head. (1) labrum, 
(2) mandibles, (3) maxilla?, 
(4) maxillary palpi, (5) labium, 
(6) labial palpi, (7) hypophar- 
ynx (?), (8) eyes, (9) antennae. 
(Redrawn after Uzel.) 





Fig. 26. — Head and mouth parts of a cone-nose, 
piercing and suctorial, with jointed proboscis. 
Hemipteron type. A. side view of head showing 
(1) portion of antenna, (2) compound eye, 
(3) ocellus, (4) clypeus, (5) jointed labium, 
(6) protruding setae or piercing bristles, consisting 
of the mandibles and maxillae. B. Shows setae 
withdrawn from labium. (7) mandibles, (8) max- 
illae, (9) hypopharynx. 

piercing and are suctorial in function. 



28 



MEDICAL AND VETERINARY ENTOMOLOGY 




Fig. 27. — Head and mouth parts 
of a mosquito (Culex sp.). Il- 
lustrating the generalized Dip- 
teron type of mouth parts (first 
subtype) with maximum num- 
ber (six) of bristle-like stylets. 

(1) Nematoceran antenna?; 

(2) compound eyes ; (3) clypeus ; 
(4) labium ; (5) labella ; (6) man- 
dibles ; (7) maxilla ; (8) maxil- 
lary palpi ; (9) labrum ; (10) 
hypopharynx. 



Hemipteron Type. — A very different 
sort of organ than those above described 
is found in the Hemiptera (Fig. 26). Here 
the labium forms a prominent beak which 
is usually three (rarely one or four) jointed 
and telescopic. This beak incloses a pair 
of mandibles, often provided with terminal 
barbs, and a pair of maxillae, all stylet-like 
and of great efficiency in piercing the skin. 
The maxilla? are more or less completely 
joined, forming a tube, so that only three 
stylets can be seen on examination. The 
labrum is quite short and inconspicuous. 

Dipteron Type. — (a) First Subtype, 
the Mosquito. — The most generalized type 
of Dipteron mouth parts is found in the 
mosquito (Fig. 27), hence here we find the 
maximum number of stylets representing 
the structures of the more generalized type, 
loosely ensheathed within the elongated 
labium, the whole forming a prominent 
beak or proboscis. The identity of the 
six stylets is not well established, though 
it is generally accepted that they represent 
the two mandibles, the two maxilla (dis- 
tinctly serrated distally), the hypopharynx , 
and the labrum-epipharynx. The palpi 





Fig. 28. — Head and mouth parts of a horsefly (Tabanus). The maximum number of 
parts is retained, but the piercing structures are distinctly blade-like. Dipteron type, 
second subtype. A. Side view of head showing (1) antenna (brachycerous), (2) com- 
pound eye, (3) labium, (4) labella, (5) maxillary palpus. B. Piercing structures ex- 
posed, labium removed. (6) mandibles, (7) maxillae, (8) hypopharynx, (9) labrum- 
epipharynx. 



INSECT MOUTH PARTS 



29 



are conspicuous structures in all mosquitoes and are useful as a means 
for identification. These represent the 
maxillary palpi of the grasshopper, while 
the pair of flattened lobe-like organs 
forming the distal portion of the pro- 
boscis are said to represent the labial 
palpi and are called the lobelia. 

(b) Dipteron Type, Second Subtype, the 
.Horsefly. — While retaining the same 
number of parts as the mosquito, this 
subtype is distinctly characterized by 
its flattened blade-like condition (Fig. 
28). That these mouth parts serve 
primarily as cutting structures is evident 
from the quantity of blood usually drawn 
by the " bite " of a horsefly, especially 
one of the larger species such as the black 
horsefly (Tabanus atratus). The labium 
is the conspicuous median portion loosely 
ensheathing the blades and terminating 
in large lobelia. The mandibles are dis- 
tinctly flattened and saber-like, while the 
maxill® are narrower and provided with conspicuous palpi. The 
hypopharynx and labrum-epipharynx are both lancet-like. In the male 




Fig. 29. — Head and mouth parts 
of the stable fly (Stomoxys calci- 
trans) . Stylets reduced in num- 
ber, closely ensheathed by the 
labium. Dipteron type, third 
subtype. Side view. (1) antenna, 
(2) compound eye, (3) labium, 
(4) labella, (5) labrum, (6) hypo- 
pharynx, (7) maxillary palpi. 



*« 



*.#' 





Fig. 30. — Head and mouth parts of the house fly (Musca domestica). Piercing stylet 
rudimentary. Muscular fleshy proboscis not suited for piercing the skin of higher 
animals. Dipteron type, fourth subtype. A. Side view. (1) Antenna, (2) compound 
eye, (3) labium, (4) labella, (5) labrum, (6) hypopharynx, (7) maxillary palpi ; 
B. Front view of proboscis. 



30 



MEDICAL AND VETERINARY ENTOMOLOGY 



these piercing parts are very weakly developed and are not useful as 
weapons of attack. 

(c) Dipteron Type, Third Subtype, the Stable Fly. — This subtype 
(Fig. 29) is represented by a group of flies in which the mouth parts are 
distinctly specialized for piercing, and show, together with the next 
subtype, to what extent these structures may become differentiated 
within the same family of insects. 

The proboscis at rest is carried at the position of a bayonet at charge, 
and is therefore provided with a prominent muscular elbow or knee. 





Fig. 31. — Head and mouth parts of the honeybee (Apis mellifera). Both types of mouth 
parts well developed but the mandibles are used chiefly for portage and modeling. 
(Hymenopteron type.) A. Front view of the head showing (1) antennae, (2) com- 
pound eyes. (3) simple eye, (4) labrum, (5) mandibles, (6) maxilla? (lacinia), (7) labium 
(palpi only), (8) hypopharynx ( ?) ; B. Mouth parts removed to show the parts, (5) man- 
dibles, (6) maxilla? (lacinia), (7) labium (palpi only), (8) hypopharynx (?), (9) bouton, 
(10) maxillary palpus, (11) mentum, (12) submentum, (13) cardo, (14) stipes. 

This conspicuous organ (the proboscis) is the labium terminating in the 
lobelia, which are provided with a complex series of cutting and adhesive 
structures. Within the folds of the labium and easily removable through 
the upper groove lie two setae, the labrum, the uppermost and heavier 
stylet, and the hypopharynx, a lower and weaker one, the two forming 
a sucking tube supported within the folds of the labium. The maxillary 
palpi are located at the proximal end of the proboscis. 



INSECT MOUTH PARTS 



31 



(d) Dipteron Type, Fourth Subtype, the House Fly. — Here (Fig. 
30) the prominent fleshy proboscis consists mainly of the labium, which 
terminates in a pair of corrugated rasping organs, the lobelia, and is 
attached in elbow-like form to the elongated head. The entire structure 
is highly muscular and may be either protruded in feeding or partially 
withdrawn while at rest. Lying on top of the grooved labium is the in- 
conspicuous prolonged spade-like labrum, which forms, with the hypo- 
pharynx, a sucking tube, supported by the labium, which latter also in- 
closes the salivary canal. By an examination of the labrum it will be 
seen that it forms a kind of convex covering to the concaved hypopharynx, 
thus giving rise to a food tube. The maxillse have evidently become 
fused with the fleshy elbow of the proboscis and only the prominent 
maxillary palpi remain. 

Hymenopteron Type. — In this type the two general classes of 
mouth structures, the Mandibulate and Haustellate, find a rather strong 
development in the same species, though the mandibles are not in- 
volved in the feeding process. The honeybee (Fig. 31) serves as a 
representative species. The labrum is narrow and quite simple, the 
mandibles are easily distinguishable and are useful wax implements. 
In ants the mandibles are 
highly efficient carrying organs 
and weapons of defense. The 
maxilla? form the lateral con- 
spicuous wings of the suctorial 
parts ; the lacinia and galea 
are fused and the maxillary 
palpi are minute. The labium 
is represented by the long 
structures to the right and left 
of the middle tube which is 
probably the hypopharynx. 
The hypopharynx terminates 

a spoon-like labellum or 




in 



Fig. 32 



Head and mouth parts of a butterfly 
(Vanessa sp.). (a) Side view. Suctorial, coiled 
tube, Lepidopteron type. (1) antenna?, (2) com- 
pound eye, (3) proboscis, consisting only of the 
galeae, (4) labial palpus. (The labrum is not 
visible in side view.) (b) Section of proboscis 
showing double nature. 



bouton which completes the 
lapping character of the sub- 
type. 

Lepidopteron Type. — This 
type, represented by the com- 
moner butterflies and moths, is typically a coiled, sucking tube capable 
of great elongation. Taking the cabbage butterfly (Pontia rapw) as an 
example (Fig. 32) the labrum is seen to be greatly reduced, the mandibles 
absent. (These may be weakly present in the lower Lepidoptera.) 
The maxillae are apparently only represented by the galea?, which by 
close approximation of their inner grooved surfaces form the long coiled 
proboscis. The double structure of the proboscis can be easily demon- 
strated by manipulation. The labium is represented by the labial palpi. 



32 MEDICAL AND VETERINARY ENTOMOLOGY 

Orders of Insects Arranged According to Mouth Parts with Type 
of Metamorphosis Indicated 

I. Orthopteron type. 1 Biting or chewing mouth parts. 

1. Order Thysanura, — Bristletails, springtails, et al., mouth parts with- 

drawn in cavity of head ; primitive metamorphosis. 

2. Order Ephemerida, — May flies, — mouth parts vestigial ; simple 

metamorphosis. 

3. Order Odonata, — Dragon flies and damsel flies, — simple metamor- 

phosis. 

4. Order Plecoptera, — Stone flies, — simple metamorphosis. 

5. Order Isoptera, — White ants, — simple metamorphosis. 

6. Order Corrodentia, — Book lice, et al., — simple metamorphosis. 

7. Order Mallophaga, — Biting lice, — simple metamorphosis. 

8. Order Orthoptera, — Grasshoppers, cockroaches, et al., — simple meta- 

morphosis. 

9. Order Euplexoptera, — Earwigs, — simple metamorphosis. 

10. Order Neuroptera, — Dobson flies, ant lions, aphis lions, et al., — com- 

plex metamorphosis. 

11. Order Mecoptera, — Scorpion flies, — mouth parts prolonged into a 

beak with mandibles at the tip ; complex metamorphosis. 

12. Order Trichoptera, — Caddis flies (moth-like) ; complex metamor- 

phosis. 

13. Order Coleoptera, — Beetles, — complex metamorphosis. 

II. Physopodan type. Biting in structure but sucking in function ; represents 
a transitional form between the biting and sucking insects. 

14. Order Physopoda, — Thrips, — simple metamorphosis. 

III. Hemipteron type. Elongated, typically 3 or 4 segmented proboscis (un- 

segmented in the true lice), snugly enclosing stylet-like organs; 
piercing and suctorial. 

15. Order Hemiptera, — Cicadas, bedbugs, cone-noses, et al.; simple 

metamorphosis. 

IV. Dipteron type. Unsegmented proboscis, which may or may not contain 

piercing stylets. 

16. Order Diptera, — mosquitoes, flies, et al. ; complex metamorphosis. 

a. First subtype. — The mosquito, — loosely ensheathed, piercing, 

delicate, stylet-like structures, six in number, suctorial. 

b. Second subtype, — The horse fly, — piercing, blade-like structures, 

six in number ; suctorial. 

c. Third subtype, — The stable fly, — closely ensheathed, piercing, 

heavy, stylet-like structures, two in number ; suctorial. 

d. Fourth subtype, — The house fly, — fleshy, non-piercing ; suctorial. 

17. Order Siphonaptera, — Fleas, — piercing mouth parts closely related 

to second subtype ; complex metamorphosis. 
V. Hymenopteron type. For feeding purposes the mouth parts are of a non- 
piercing, lapping type, but for purposes of combat and portage 
the mandibles are well developed. 

18. Order Hymenoptera, — Ants, bees, wasps, et al.; complex metamor- 

phosis. 
VI. Lepidopteron type. Proboscis in the form of a greatly elongated coiled 
tube ; non-piercing, suctorial. 

19. Order Lepidoptera, — Moths and butterflies ; complex metamorphosis. 

1 The term "Orthopteron" is here merely applied to indicate a type which 
varies considerably in the Order Orthoptera. 



CHAPTER V 
HOW INSECTS CARRY AND CAUSE DISEASE 1 

Environmental Considerations. — Manifestly it is necessary to know 
under what environmental conditions pathogenic organisms naturally 
exist in order to ascertain how the insect becomes infected and in turn 
is able to infect man or beast. Two factors must be considered in this 
connection, first, the natural longevity of the pathogenic organism, and 
secondly, the degree of virulence of the same when away from the normal 
host. For example, bubonic plague is a bacterial disease, traceable to 
Bacillus pestis, of which the rat is an important host. From this host, 
fleas (which are provided with piercing and sucking mouth parts) become 
infected and in the bodies of these insects the bacilli multiply and remain 
virulent ; now if such infected fleas find their way to human beings, these 
latter in turn may become infected. It may be seen that certain environ- 
mental conditions must be considered in this connection; namely, in 
what part of the body of the rat are the buboes (plague lesions) found, 
and does this correspond to the distribution of the flea on the host ; and 
if the flea sucks up plague bacilli, how long will these remain virulent ; 
will this be long enough for the insect to leave its first host, find and 
infect a second host? Then again the question arises as to how the 
plague bacilli are introduced into the body of the human being. Is the 
flea the only means of dissemination ? These are questions which, with 
others, must be answered for each case. 

On the other hand malarial fever is traceable to a protozoon 
(Plasmodium) which cannot exist in a living condition away from 
the human body except in the Anopheline mosquito. Its normal envi- 
ronment is very restricted. In the human being it is a blood parasite, 
requiring a blood-sucking insect or other mechanical means to extract 
it together with blood. Manifestly there are many blood-sucking 
insects which could withdraw parasitized blood. It has, however, been 
abundantly proved that malaria parasites cannot reproduce sexually 
except in the bodies of Anopheline mosquitoes ; in all other insects the 
parasites perish. 

Similar examples involving environmental peculiarities might be 
cited; for example, in tuberculosis, a bacterial disease, the causative 
organism (Bacillus tuberculosis) occurs largely in a transmissible infec- 
tive form away from the body in sputum. On the other hand African 

1 Students not familiar with the classification of bacteria and protozoa are 
referred to the appendix. 

33 



34 MEDICAL AND VETERINARY ENTOMOLOGY 

sleeping sickness, caused by a protozoon {Trypanosoma gambicnse), 
occurs both in the blood of humans and certain native animals 
(reservoirs), and is carried by a blood-sucking fly, the tsetse fly ; again, 
anthrax, a bacterial disease (traceable to Bacillus anthracis), if in the 
pustular form may be transmitted by blood-sucking flies of the family 
Tabanidse (horseflies), as well as in other ways, while Texas cattle 
fever, traceable to a protozoon (Babesia bigemina), is transmitted 
solely by the tick, Margaropus annulatus, in which infection is hereditary. 

These few examples will serve to show the necessity for having a 
working knowledge of the pathogenic members of the two great groups 
of unicellular organisms, namely the Bacteria and the Protozoa. In gen- 
eral it may be said that the longevity and pathogenicity of the Bacteria, 
when outside the host is considerably greater than in the Protozoa, 
owing to the highly specialized environment required by the latter. 

How Insects Carry Disease. — The simplest way in which insects 
enter as a factor in the transmission of disease is by means of soiled feet 
and mouth parts. Any insect might accidentally become contaminated 
with infective sputum or fecal matter and in turn might accidentally 
come in contact with human foods, thus becoming an indirect factor in 
transmission. In this connection the normal habit of the insect must 
be considered, i.e. its breeding habits, food habits and general behavior. 
Thus the house fly enters as a factor in the transmission of such diseases 
as typhoid fever and dysentery, because of its naturally filthy habits. 

A second purely mechanical method of disease transmission, though 
more restricted, is by means of a soiled piercing proboscis, in cases of 
certain parasitic blood diseases. In the first-mentioned method the 
type of mouth parts does not figure as a restrictive factor, but in the 
second method, in order that the proboscis may become soiled with 
blood, the mouth parts must be capable of piercing the skin, thus coming 
in contact with the blood and its contained parasites, if present. The 
inoculation of the second host may be purely mechanical. Insects that 
belong to this class of carriers ordinarily have heavy piercing mouth parts 
capable of drawing considerable blood, are intermittent parasites and go 
from host to host within a short space of time. The horsefly (Tabanus) 
is a good representative of this class in its chance relation to anthrax. 

A more highly complicated method is involved in the transmission 
of bubonic plague by fleas. In this case the carrier has piercing mouth 
parts, is blood-sucking and an intermittent parasite. The plague bacilli 
when taken into the stomach of the flea multiply and do not become 
attenuated, but pass out per anum with the feces or even in undigested 
blood; the direct inoculation is accomplished by a "rubbing in" 
process either on the part of the host or flea. Infection may also take 
place by regurgitation in the act of biting. 

The greatest complexity is involved in those cases in which the insect 
carrier is a necessary intermediary host oj the pathogenic organism, e.g. the 
Anopheles mosquito in its relation to malaria. A given period of time 



HOW INSECTS CARRY AND CAUSE DISEASE 35 

must elapse after the mosquito imbibes infective blood before it can trans- 
mit the causative organism. This period corresponds to the time 
required for the plasmodium to pass through its sexual cycle in the 
stomach of the mosquito and find its way into the salivary glands, ready 
to be inoculated into the blood of the mosquito's next victim. 

How Insects Cause Disease. — ■ Insects and arachnids may relate 
to pathological conditions, whether serious or of little consequence, in 
one or more of the following ways : first, by direct infection; second, 
by indirect infection; third, by internal parasitism; fourth, by external 
parasitism; and lastly, by venoms. The same species may fall as 
legitimately into two divisions, as for example, the Texas fever tick, 
which if not infected with the causative organism of the fever need only 
be considered as an external parasite, but when the causative fever organ- 
isms are present in the tick, would relate it also to direct infection. 

Direct Infection. — Direct infection under ordinary conditions could 
only be produced by an insect or arachnid possessing piercing mouth 
parts, and here no special order or larger group can well be referred to, 
inasmuch as closely related insects may have very different mouth 
structures . The common house fly and the stable fly, for example, belong 
to the same family (Muscidse), therefore are closely related, yet have 
widely different mouth parts ; though both are suctorial, the former is 
unable to pierce the skin, whereas the latter can do so with ease. 

By direct infection is meant the introduction of a pathogenic organ- 
ism, whether bacterial or protozoan, into the circulation of a higher 
animal. The Anopheles mosquito is therefore related to this manner 
of transmission, because it introduces the malaria parasite (Plasmodium) 
directly into the blood stream of man. The same is true of the Steg- 
omyia (TEdes) mosquito and yellow fever ; the Glossina flies and sleep- 
ing sickness; horseflies and anthrax. Direct infectors are usually 
temporary, intermittent ectoparasites permitting transfer of activity 
from animal to animal. 

However, there is still a possibility for an insect with mandibulate 
mouth parts or with non-piercing haustellate mouth parts to infect an 
animal as directly as one possessing piercing mouth parts. Thus the 
house fly may, by means of its feet and mouth parts, transmit septicaemic 
infection to an animal undergoing surgical operation or suffering from 
an open wound. 

Indirect Infection. — This form of infection relates chiefly to enteric 
diseases in the causation of which the pathogenic organism is deposited 
upon food by the insect. Thus the food is first infected and with it the 
pathogenic organism is implanted within the alimentary canal of the 
victim ; in this way the insect is only concerned indirectly. The house 
fly, one of the grossest transmitters of enteric diseases, is only so because 
of accident of habit and structure, feeding as it does indiscriminately 
on excrement and food of higher animals, and with proboscis and feet 
so constructed as to certainly collect germ-laden particles of excrement. 



36 MEDICAL AND VETERINARY ENTOMOLOGY 

Insects possessing mouth parts not adapted to piercing the skin 
(whether biting or sucking) may relate to this form of infection, and 
indeed any insect or arachnid may be an indirect carrier by accident. 
Furthermore, insects ordinarily relating only to indirect infection may 
produce direct infection of certain kinds where there is access to an open 
wound as already explained. 

Internal Parasitism. — There are no insects so far as is known 
which spend their entire life history in the form of internal parasites. 
There are, however, a number which pass their larval period (period of 
growth) within the alimentary canal or in the muscle tissue of higher 
animals. The best-known representatives of this group are the botflies 
and the warble flies, the former found in the stomach and intestine of 
equine animals, while the latter are found in the muscle tissue of bovine 
and equine animals, rodents, and sometimes man. The harm done by 
internal insect parasites is of various kinds, e.g. irritation, impaired 
digestion, loss of nutrition, etc. 

External Parasitism. — The most important and most abundant 
external parasites of man and of the domesticated animals are found 
among the insects and arachnids. Very serious and often fatal results 
are due to this form of irritation, and the loss of blood due to an abun- 
dance of blood-sucking species must not be overlooked. External 
parasites may be either permanent or temporary in relation to the 
host. The commonest permanent parasites are the biting and sucking 
lice, which are usually transferred from host to host by close association 
of mammals while sleeping together in close quarters, or while in copu- 
lation ; in poultry generally while roosting. The sucking lice are also 
important disease vectors, w T hich involves transfer of activity from 
animal to animal, usually brought about by close association, inter- 
change of garments and toilet articles. Thus lice are carriers of 
typhus fever and relapsing fever, infection being brought about by the 
bite or by crushing the parasites and scratching or " rubbing in " the 
infective agent. Temporary intermittent ectoparasites are the most 
important of all disease carriers, owning to their habit of changing hosts. 
It may well be seen that herein lies the danger of transmitting infec- 
tious diseases from animal to animal. The temporary ectoparasites are 
well represented by the fleas, bedbugs and certain ticks. 

Insect Venoms. — Another form of irritation is produced by the 
introduction of a specific venom by contact, pierce or sting. Many 
insects produce severe irritations by their bites, which fact can be ac- 
counted for by the presence of a venom-secreting gland, often salivary. 
The cone-noses or kissing bugs (Reduviidse) inflict a very painful wound 
aggravated by a poison ; other insects produce nettling when handled, 
e.g. the blister beetles (Meloidee) ; and the familiar sting of the bee 
(Apidae) and wasp (Vespidse) is chiefly painful because of the injection 
of specific poisons. 



CHAPTER VI 
COCKROACHES — BEETLES — THRIPS 



A. The Cockroaches 
Order Orthoptera, Family Blattidce 

Few insects excepting the lice are looked upon with as much disgust 
as are the cockroaches. The mere suggestion that these insects might 
be present in a dwelling or place of business leads usually to a rough 
snubbing. Such is the experience of inspectors whose duty it is to keep 
a record of vermin and noxious insects in connection with health move- 
ments in certain cities. A flat denial 
is often forthcoming in the face of 
the strongest evidence. 

Habits. — Cockroaches belong to 
that group of insects which attack 
human food in all degrees of prepara- 
tion. Not only human food but all 
manner of organic material is at- 
tacked ; nothing seems to be exempt, 
as all will attest who have spent 
some time in tropical or subtropical 
sections in particular. They are 
omnivorous, with a special incli- 
nation toward starchy and sugary 
materials. Where everything seems 
to be shipshape during the daytime, 
at night one can hardly take a step 
without hearing that ominous crackling underfoot as these creatures 
are crushed by the tread. During the day the cockroaches are in 
hiding in dark corners, behind wainscoting, under boxes, in cupboards 
and the like, regardless (yes, perhaps with predilection) of filth. 

Life History. — There seems to be little difference in the life history 
of the various species of cockroaches. The female is often seen with a 
chestnut-colored, chitinous object (Fig. 33), partly protruding from the 
terminal abdominal segment. This is the egg case, or oothecum, which 
is carried around by the female often for several weeks until the 
young are ready to hatch. These egg cases appear at all times of the 
year, hence it seems that there is no special season to which egg 

37 




Fig. 33. — Egg cases (ootheca) of cock- 
roaches, (a) oriental roach ; (6) cro- 
ton bug. X 3. 



38 



MEDICAL AND VETERINARY ENTOMOLOGY 



deposition is limited. The young roaches are quite active from the 
beginning, having the same food habits as the adults. Their 




Fig. 34. — The croton bug (cockroach), Blatella (Ectobia) germanica, in various stages of 
development. The adult female is shown with egg case or oothecum in normal posi- 
tion protruding from the terminal abdominal segment. X 2. 



metamorphosis is simple, quite like that of the grasshopper, requiring 

about one year to reach maturity, prob- 
ably somewhat less in tropical and 
subtropical countries. The writer has 
kept cockroaches (the croton bug) 
under observation in glass jars for 
many weeks in order to note their 
growth, which was seen to be very 
slow. As the individuals molt, the 
shed skins are eaten, as are also the 
dead roaches, — an economical habit. 
Structural. — Cockroaches have 
characteristically, dorsoventrally, flat- 
tened bodies, generally of a chestnut 
brown to black color. The wings of 
the males are usually well developed, 
but the females often have mere ves- 
tiges. While the winged forms pos- 
sess the power of flight, the group as 
a whole is running in habit and the 
individuals can cover ground in this 
The mouth parts are of the biting 




Fig. 35. — The oriental roach, Blatta 
orientalis. X 1.3. 



way with marvelous rapidity, 
type, distinctly orthopteron. 



COCKROACHES — BEETLES — THRIPS 



39 



Species and Distribution. — As household pests cockroaches are 
widely distributed, brought about chiefly through maritime trading; 
holds of vessels as well as the crew's sleeping quarters are oftentimes over- 
run with these miserable pests. The most widely distributed species 
are the croton bug, Blatella germanica Linn. (Fig. 34), and the oriental 
roach, Blatta orientalis Linn. (Fig. 35). The former is one of the small- 
est species, measuring about five-eighths of an inch to the tip of the 
wings, which are present in both sexes. This species is evidently the 
most common form along the north Atlantic and north Pacific coasts, 
as shown by observations made in Boston, New York and San Fran- 
cisco. The name croton bug has 
been applied to this insect because of 
its appearance during the construc- 
tion of the Croton water system of 
New York City. In color the in- 
sect is a muddy brown with two 
longitudinal stripes on the pronotum. 

The oriental roach is an inch or 
more in length and is very much 
darker than the croton bug, hence 
is often called " black beetle " (the 
term beetle being wrongly applied). 
The female has vestigial wings, while 
in the male these organs are short, 
reaching not quite to the tip of the 
abdomen. This form is more com- 
mon in the central states of the 
United States and according to Kel- 
logg extends as far west as the great 
plains. It also occurs in California. 

Another house-infesting species is 
the native American cockroach, Peri- 
planeta americana Linn. (Fig. 36), a 
light chestnut-colored species, which reaches a length of an inch and a 
half and has long wings in both sexes. This is also a common species 
in the middle and western states, being especially abundant in Mexico 
and Central America. It resembles a slightly shorter species occupy- 
ing about the same territory in the United States, namely, Periplaneta 
australasioB Fabr. (Fig. 37), which differs further in that the Austra- 
lian roach has a yellowish border around the pronotum, extending partly 
down the outer margins of the wing covers. Our commonest native 
outdoor species is Ischnoptera pennsylvanica De G. To these common 
forms might be added a list of exotic roaches constantly coming to 
our shores on shipboard from the Orient and elsewhere, but which have 
never secured a foothold. 

Life History and Habits of the Croton Bug. — The croton bug is 





if H 




/ 1 


f: \ m 




I 

■/ J 








^1 


^B 1 ij, 


HP 




f yw 






\ 



Fig. 36. — The American cockroach, 
Periplaneta americana. X 1.3. 



40 



MEDICAL AND VETERINARY ENTOMOLOGY 



nocturnal in habit, but may be seen roaming about during the day, 
although its activity is then limited. Generally the roaches collect in 
huddled groups during the day and remain inactive. Their main 
requirements for activity are, first, a fairly high temperature ; secondly, 
darkness; and lastly, a supply of food. Roaches are commonly en- 
countered in kitchens, galleys, restaurants, bakeries, etc. These in- 
sects are omnivorous, favoring starchy and sweet materials ; they may 
also feed on excrement and will readily devour their dead brethren 
and cast-off skins. 

The eggs of the roach are laid in pairs (13 pairs usually) in an egg case, 
or oothecum (Fig. 34), which, when filled, protrudes from the abdomen 

of the female. The females may evi- 
dently carry these cases about with 
them two months or more, when they 
are finally deposited in some dark 
crevice, and the young roaches or 
nymphs hatch out in twelve days or 
less. The young roaches are at first 
almost white and transparent, but 
soon become brownish and resemble 
the adults except for size and absence 
of wings. The young roaches molt 
soon after emergence from the egg 
case and again in about four weeks. 
There are apparently about six molts 
before the roaches are mature, and 
Fig. 37. — The Australian roach Pen- certainly a year or more is required 

planeta australasiee. X 1.12. •, « , ■. . • t i j 

before this is accomplished. 

Relation to Disease Transmission. — Cockroaches have long been 
looked upon with some suspicion as possible carriers of disease and are 
certainly regarded with much disgust by everybody. If the house fly 
is such a potent transmitter of infection, why not the cockroach, at least 
to a large degree ? While the house fly is active in the daytime, walking 
over prepared human food, depositing thereon its load of bacteria, the 
cockroach is actively engaged, under cover of night, in a similar per- 
formance. The two insects by analogy must relate to the transmission 
of bacteria in a similar manner, i.e. must collect bacteria on their feet 
and mouth parts by crawling and feeding on filth which may be 
charged with bacteria, and depositing these on human food, while in 
the act of feeding. 

The cockroach has biting mouth parts like the grasshopper, hence 
could not relate to the transmission of disease by direct inoculation, as 
does the stable fly, for example, which has piercing mouth parts. If 
the structure of the cockroach is such that it can pick up bacteria easily, 
and if it can be shown that the cockroach invades places where infective 
material, such as sputum or excrement, is found, then a chain of strong 




COCKROACHES — BEETLES — THRIPS 41 

circumstantial evidence could be produced that the roach is a factor in 
the dissemination of such diseases as tuberculosis, dysentery, cholera and 
probably typhoid fever. The food habits of the roach are certainly such 
that there is ample opportunity for the contamination of the food of man. 

Comparing the feet and mouth parts of the house fly and the croton 
bug, it will be seen at once that the latter is far less adapted to the col- 
lection of filth, inasmuch as the feet, especially, are not so well provided 
with spines and hairs as are the feet of the house fly. However, the 
weight of the insect and surface in actual contact with infective mate- 
rial partly compensates for the above structural deficiency. 

Can the Roach Pick up Specific Bacteria ? — In order to answer 
this question one of these insects was allowed to crawl over a culture of 
Bacillus pyocyaneus aureus, a green chromogen, in a test tube. The 
growth on the agar in this tube was not very profuse. The insect was 
next transferred to a sterile agar plate upon which it was permitted to 
walk one minute. The roach was then liberated and transferred to a 
second plate for one minute, and then to a third plate in a similar man- 
ner. The agar plates were then incubated for 24 hours at a temper- 
ature of 37° C. At the end of this time a good growth of the green 
chromogen, Bacillus pyocyaneus aureus, had developed on all three plates. 

This experiment goes to prove that the legs of the roach are con- 
structed so as to enable it to pick up bacteria of a given kind and enough 
to heavily inoculate at least three plates. 

Can the Roach Carry Specific Bacteria to Human Food ? — Having 
determined that the roach can pick up known bacteria, the next thing 
was to prove that it could deposit these same organisms on human food. 
In order to do this one grain of sugar was exposed to a cockroach that 
had previously walked across an agar plate culture of Bacillus pyo- 
cyaneus aureus, the same chromogen used above. The insect remained 
with the sugar, feeding on it, for three minutes. The sugar was then 
dissolved in 5 cc. of sterile water and plated on three agar plates, using 
1 cc. of the solution for each. The plates were incubated for 24 hours 
at 37° C. B. pyocyaneus aureus was recovered on all three plates, the 
growth on none being scanty. The recovery of the test culture in the 
sugar solution showed that the contaminated cockroach could in turn 
contaminate the food over which it crawled and upon which it fed. 

The Bacterial Population of the Croton Bug. — Six individuals were 
selected from a collection of roaches taken from various localities and 
permitted to crawl for one minute over six sterile agar plates (one roach 
for each plate). These plates were incubated for 48 hours at 37° C. 
Each plate showed a good growth, the colonies on examination proving 
to be saprophytic without exception. 

To secure an approximate estimate of the number and kind of bac- 
teria carried by roaches, two of these insects were treated as follows. 
After sterilizing pipettes, forceps, tubes, etc., 5 cc. of distilled water was 
placed in each of the five test tubes. Into these tubes were placed the 



42 



MEDICAL AND VETERINARY ENTOMOLOGY 



legs and antennae of the roaches, — the posterior pair of legs of one roach 
into one tube, those of the other roach in a second tube, the antennae 
of both roaches in a third, and the remaining pairs of legs of the first 
roach in the fourth and the remaining pair of legs of the other roach in the 
fifth tube. The stomach contents were plated on agar. The tubes 
were shaken vigorously for three minutes in order to wash the parts 
well and then 1 cc. of the water in each tube was plated on agar and 
incubated 24 hours at 37° C. The results were all positive, as the fol- 
lowing table (Table I) indicates : 

TABLE I 

Showing Number and Kind of Bacteria Carried on Individuals of 

the Croton Bug 



No. OF 

THE 

Roach 


Part of the 
Roach Plated 


Bacterial 
Count per cc. 


Kind of Bacilli Present 


1 


Posterior 
pair of legs 


1200+ 


(a) Staphylococcus albus 

(b) Non-spore-bearing bacillus 


2 


Posterior 
pair of legs 


1600+ 


(a) Staphylococcus albus 

(b) Non-spore-bearing bacillus 


1 


Remaining 
legs 


950 


(a) Staphylococcus albus 

(6) Small non-spore-bearing bacillus 

(c) Spore-bearing air bacillus 


2 


Remaining 
legs 


1200 


(a) Spore-bearing air bacillus 

(b) Staphylococcus albus 


1-2 


Antennae 


384 


(a) Spore bearing air bacillus 
(6) Staphylococcus aureus 
Yellow pigment 


1 


Stomach 
contents 


14 


(a) Minute bacilli (unidentified) 




Total 


5348+ 


for a dilution of | 



5 X 5348 + -r- 2 = 13,370 + bacteria, — minimum number present on each roach 



From the above table it will be seen that each roach carried on its 
feet and antennae and in its stomach a minimum of 13,370 bacteria. 
While this does not represent a fair estimate for all roaches, since only 
two individuals were used, we are here shown that the roach can carry a 
large number of bacteria. Esten and Mason (Storrs Agric. Exp. Sta., 
Bull. No. 51) have shown that the number of bacteria carried by a fly 
range all the way from 550 to 6,600,000, with an average of one and one 
fourth million bacteria on each. Thus by comparison it may be seen 
that the roach probably carries fewer bacteria. 



COCKROACHES — BEETLES — THRIPS 43 

It is furthermore interesting to note that there were more bacteria 
on the single pair of posterior legs than on the remaining two pairs com- 
bined. This is probably explained by the use the cockroach makes of 
its hinder pair of legs. The tibia? and tarsi are in contact with the sur- 
face on which the insect walks, being parallel with the body. Very often 
the insect stands on the hind pair of legs, with the remaining legs barely 
touching the surface. The fore legs are also frequently brushed by the 
antenna?. 

Environmental. — The last link in the chain of evidence against the 
cockroach is its normal environment, which gives the insect an oppor- 
tunity to contaminate itself with pathogenic organisms, if present. 
Such an environment would be an accessible insanitary privy, close to 
the kitchen or pantry, in which case there is at least the possibility'of 
the transference to the food of man of one of the causative organisms 
(bacillary) of dysentery, diarrhea and cholera and still more remotely 
of typhoid fever. 

Conditions favoring the transmission of the tuberculosis bacillus 
are relatively more common. Two instances may be cited. These 
existed in the forecastle of two vessels. On these two vessels no sepa- 
rate mess rooms were provided for the sailors, their food being served 
in the same room in which they slept. Bread, butter and sugar were 
usually left uncovered on the table, readily accessible to cockroaches, 
which swarmed over floors and walls. Sailors occupying the rooms were 
in the practice of constantly spitting on the floor. If one or more of 
these sailors should be tubercular, there is at least the possibility of germ 
transmission by the roach to the food. A third instance may be men- 
tioned, that of a certain roach-infested residence occupied by a con- 
sumptive in the last stages of the disease. This patient did not use 
sputum cups, and although belonging to a refined family had the per- 
nicious habit of spitting in the darker corners of the room and behind 
pieces of furniture. In this house lived a half dozen students who also 
took their meals there. Roaches were commonly seen in the room in 
which the patient lived and roaches swarmed in the pantry and kitchen 
at night. Surely here existed a condition that favored the transmission 
of tubercle bacilli. Unfortunately the reputation of this house in one 
of the more select districts of the city was of more importance than 
the lives of the inmates of the house. 

Other Considerations. — The fact that roaches also feed on fecal 
matter may lead to further complications, which, owing to lack 'of 
experimental evidence, cannot be considered here further. However, 
it was very early known that cockroaches may become infected with 
FUaria ryti pi eu rites Delonchamps of the rat, by feeding on rat feces, 
and that other rats may become infected in turn by feeding upon such 
roaches. Galeb in Comprend Rendu (1878) reports his observations 
upon the transmission of this nematode. He discovered numerous 
parasites in the " adipose tissue " of the roach Blatta orientalis, which 



44 MEDICAL AND VETERINARY ENTOMOLOGY 

were found to be identical with nematodes found in the rat, Mus de- 
cumanus. He also found hair of the rat in the alimentary canal of the 
roach. On feeding rats (Mus rattus) with infected roaches and examin- 
ing them after the expiration of eight days, he found the parasites in the 
folds of the mucous membrane of the stomach. Several nematodes 
(three females and one male) had already developed sexual organs. 
More recent experimental evidence indicates that the roach is almost 
certainly the intermediary host of this nematode. 

Control. — Numerous methods have been evolved to combat the 
cockroach, and it is quite certain that this insect can be controlled in 
dwellings, restaurants and the like. One method which has been found 
useful for the larger less abundant form is the trap. This consists of a 
deep, smooth-walled vessel (fruit jar or the like) into which is placed a 
favorite roach food, such as chocolate, or molasses (stale beer or ale are 
also recommended) . Sticks leading to the top of the jar must be provided 
in order that the roaches can easily reach the mouth, and in their en- 
deavor to get at the food tumble into the trap. If there is a liquid in 
the trap, the roaches are drowned; otherwise they must be killed by 
scalding. 

Trapping methods are least successful in the control of the croton 
bug; it is certainly far more wary than the larger species. The ordi- 
nary glass-jar-trap method employed for the larger species is not effec- 
tive. The croton bug can crawl up the sides of a glass jar without diffi- 
culty and thus make its escape. A dark box trap is preferable with one 
or more tubular pasteboard entrances projecting both inside and out- 
side. The mouth of the tube inside the box must be guarded either with 
a single trap door or adhesive substance around the outside of the tube 
and immediately adjacent to the mouth to prevent the roaches from 
escaping after feeding on the bait. The box may be baited with sugar, 
sweet chocolate, a little stale beer or the like. After the roaches have 
been captured they are shaken out through a lid into kerosene or 
hot water. The box is then once more baited and placed in posi- 
tion. 

More satisfactory results are obtained by means of poisons. When 
the word poison is used in this connection it does not necessarily imply 
that it is a poison also to human beings, since there are some materials 
which act in this way when eaten by insects but are non-poisonous to 
human beings, except, of course, when taken in large quantities ; among 
such materials are borax and formalin. Borax is frequently used as an 
ingredient in the preparation of roach and ant poisons. Thus equal 
parts of chocolate, or powdered sugar, and borax well mixed (this is 
important) provide an excellent roach powder. This powder should 
be placed in little heaps or in windrows easily accessible, or may be 
sprinkled in the crevices whence the insects come. Persian insect 
powder or pyrethrum stupefies the insects. Dusting the haunts of the 
roach liberally with flowers of sulphur also proves effective as a re- 



COCKROACHES — BEETLES — THRIPS 45 

pellent. Two methods mentioned by Felt l are the following : " The 
smoke of burning gunpowder is very obnoxious and deadly to roaches, 
particularly the English roach. The moistened powder should be 
molded into cones, placed in an empty fire-place and ignited. It is 
particularly valuable in the case of old houses." A second method, 
viz. : " A relatively simple method, described by Mr. Tepper of 
Australia, is to mix plaster of paris, one part, and flour three or four 
parts, in a saucer and place the preparation about the haunts of the 
pests. Near by there should be a saucer containing a little water and 
made easily accessible to the roaches, laying a few sticks as bridges up to 
the rim . The insects eat the mixture, drink the water and soon succumb . ' ' 
Fumigation with hydrocyanic acid gas, carbon bisulphid or sulphur 
may be resorted to with much success ; however, should not be under- 
taken without experienced assistance, since the behavior of these gases 
must be fully understood. 



B. The Beetles 
Order Coleoptera 

The beetles may easily be distinguished from other insects by the 
following characters : the mouth parts are of the biting type, mandi- 
bles strongly developed ; two pairs of wings are present of which the for- 
ward pair is hardened and does not overlap at the tip ; the ventral por- 
tion of the abdominal segments consists of chitinous plates extending at 
least halfway round the body. (In other insects these ventral plates 
are much shorter as a rule.) 

The metamorphosis of Coleoptera is complex (egg, larva, pupa, 
imago) with the occurrence of hypermetamorphosis in a number of 
species. The larvae of this order are commonly called " grubs " and 
may be recognized by the presence of three pairs of rather feeble legs. 

Only a few families of this great order of insects concern us, and only 
those which by habit come in contact with diseased animal carcasses, 
or attack other living animals or which possess medicinal properties. 

Scavenger Beetles. — All the scavenger beetles are of interest in 
this connection since the habit of feeding on dead animal matter 
might accidentally bring them in contact with the infection. Infec- 
tion may be carried in two ways, namely, first mechanically on the 
body, legs or mouth parts, or secondly, in the excreta. The latter 
method involves attenuation in that the pathogenic organism may 
become reduced in virulence in its passage through the alimentary canal 
of the insect. 

Among the families of scavenger beetles are the Staphylinidse or rove 
beetles (not all animal feeding), recognized by the abbreviated condition 

1 Felt, Ephraim Porter, 1909. Control of Household Insects. New York 
State Museum, Bulletin No. 129 (Albany). 



46 



MEDICAL AND VETERINARY ENTOMOLOGY 




Fig. 38. — ■ Rove beetles (Staphylinidse) 
a. Creophilus ; b. Staphylinus. X 1.5. 



of the wing covers (elytra), thus exposing the abdomen dorsally, and 
giving these beetles a larval or worklike appearance, augmented by the 
flexibility of these parts. The functional wings are folded up and con- 
cealed under the elytra. The range in size in this family is enormous. 
One very small species in the act of swarming is known to get into the 
eyes of people when driving, cycling or motoring, causing a severe burn- 
ing sensation by means of the vile- 
smelling body secretions. The spe- 
cies commonly met with on turning 
over carcasses, hides, heaps of bones 
and other animal rubbish, belong 
to two genera ; namely, Creophilus 
(Fig. 38 left) and Staphylinus (Fig. 
38 right), which include species 
ranging from one half to one inch 
in length. A second family to be 
considered are the Silphidae, or 
sexton beetles, also known as car- 
rion beetles. In habit these insects 
are more decidedly scavenger than 
the preceding, feeding almost ex- 
clusively on dead flesh, both as larvae and adults. Again two genera 
will serve to illustrate the commoner forms, namely, Silpha (Fig. 39 
left) and Necrophorus (Fig. 39 right). These two genera are well illus- 
trated as to relative size and general shape by the accompanying figures. 
A third family, the Histeridae, is composed of a group of small- 
sized, short, shining, black beetles commonly found about decompos- 
ing animal matter. 

The fourth family, Derm- 
estidse, also includes only small 
forms, about one third of an 
inch and less in length. In 
shape they are elliptical, usu- 
ally dark grayish or brownish 
in color. Skins and other ani- 
mal specimens in museums are 
often ruined by the museum 
pest, Anthrenus museorum 
Linn, or Anthrenus verbasd 
Linn., if proper precautions are 
not taken. This damage is practically all done by the larvae, as is the 
case with the larder beetle, Dermestes lardarius Linn, and D. vulpinus 
Fabr. and the carpet beetle, Anthrenus scrophularioe Linn. 

Relation to Disease. — Where hides taken from anthracic animals 
or the carcasses are attacked by scavenger insects it is more than likely 
that there will be danger from this source. The following statements 




Fig. 39. — Sexton beetles (Silphidae). a. Sil- 
pha americana; b. Necrophorus sp. X 1.5. 



COCKROACHES — BEETLES — THRIPS 



47 



taken from Nuttall 1 bear directly on this subject, viz. " Proust (1894), 
in examining goatskins taken from anthracic animals, found quantities 
of living Dermestes mlpinus upon them. He found virulent anthrax 
bacilli in their excrements, as also in the eggs and in the larvae. It is 
evident from this that these insects which feed on the skins permit the 
anthrax spores to pass uninjured through their alimentary tract. Heim 
(1894) also had occasion to examine some skins which were suspected 
of having caused anthrax in three persons engaged in handling the 
leather. He found larva? of Attagenus pellio Linn., Anthrenus museorum 
Linn, (both Dermestidse) and 
Ptinus, also fully developed 
insects of the latter species 
on the skins. All these in- 
sects had virulent anthrax 
bacilli (spores) on their sur- 
face and in their excreta, 
from which Heim concludes 
they might spread disease. 
He says the excreta are very 
light and easily scattered by 
the slightest current of air. 
Heim does not believe the 
bacilli multiply in the bodies 
of these insects, but that 
the latter may be dangerous 
through their scattering the 
spores about.' ' 

May Beetles and Thorn- 
headed Worms. — May beetles 
or cockchafers (Family Scara- 
bseidse) are known to be in- 
termediary hosts both in the 
larval and adult stages of the 
thorn-headed worm (Fig. 40), Echinorhynchus gigas Goeze, a parasite of 
swine also said to occur in man in rare cases. This nematode worm in 
its adult stage measures from 20 to 30 cm. in length and about 3 to 5 mm. 
in thickness, and inhabits the small intestine of its host. The eggs are 
deposited in this habitat and pass out with the feces which may be swal- 
lowed by the larvae of the cockchafers. These are often extremely abun- 
dant among the rootlets of grass in heavily sodded pastures, and swine 
with free range are exceedingly fond of these grubs, in search of which 
they diligently root up the soil with their snouts. Thus every oppor- 
tunity is given for the grubs to become infected and in turn the swine. 

1 Nuttall, George H. F. On the Role of Insects, Arachnids and Myriapods, 
as Carriers in the Spread of Bacterial and Parasitic Diseases of Man and Animals. 
Johns Hopkins Hospital Reports, Vol. VIII, Nos. 1-2, 1899. 




Fig. 40. — Thorn-headed worm, Echinorhynchus 
gigas, of swine, requiring a May beetle (Lach- 
nosterna or Melolontha) as intermediary host. 
X 1. 



48 



MEDICAL AND VETERINARY ENTOMOLOGY 




Fig. 41. — May beetles or cockchafers, Cotalpa 
lanigera (left) and Lachnosterna fusca (right). 
Serve as intermediary hosts for the thorn-headed 
worm of swine. X 1.2. 



After the ova have been ingested the larvae hatch in a few days 

within the intestine of the 
insect and proceed to 
burrow through the in- 
testinal wall and into the 
muscles, where they are 
said to encyst them- 
selves. In Europe the 
intermediary host is com- 
monly Melolontha melolon- 
tha Linn, (vulgaris Fab.) 
and Cetonia aurata Linn. 
May beetles of the genus 
Lachnosterna (Fig. 41) 
(according to Stiles, Lach- 
nosterna arcuata Smith and 
others) are probably all 
more or less concerned. 
The life history of nearly 
all May beetles is quite 

long, the larval stage alone often requiring nearly three years. 
In districts infested with the thorn-headed worm a systematic 

crusade against cockchafers 

would be the logical means of 

control, together with the 

treatment of swine with vermi- 
fuges, the swine being properly 

coralled so that the feces can 

be disinfected with formalin or 

other effective disinfectant. 
Saw-toothed Grain Beetle. 

— At least one case has been 

reported to the writer in which 

the saw-toothed grain beetle, 

Silvanus surinamensis Linn. 

(Fig. 42), of the family Cucu- 

jidse, invaded sleeping quar- 
ters, causing great annoyance 

to the occupants by nibbling 

at and crawling about on the 

body. The infestation, which 

lasted several days, was traced 

to the bathroom, thence out 

of the house through the yard 

and into an old barn under the 

stalls, where unquestionably grain from the manger had accumulated 




Fig. 42. 



The saw-toothed grain beetle, Silvanus 
surinamensis. X 33. 



COCKROACHES — BEETLES — THRIPS 49 

and where these beetles had been bred in great numbers. The dry 
California summer had pretty surely driven these insects to the bath- 
room for water, and the attack upon the occupants of the adjoining 
bedchamber was merely an incidental matter. However, it is interest- 
ing to note that an instance is recorded in Braun's Parasites of 
Man, viz. " Taschenberg records this beetle as having invaded some 
sleeping apartments adjoining a brewery where stores were kept, and 
annoying the sleepers at night by nipping them in their beds." 

Cantharidin, Spanish Fly. — Although a few other insects secrete 
vesicating fluids, the principal source for medicinal purposes is the group 
of insects known as the blister beetles (Meloida 1 ) of which the Spanish 
fly, Lytta vesicatoria Linn. (Fig. 43), is the most important member. 




Fig. 43. — The Spanish fly, Lytta vesicatoria 



This beetle is a European form found most abundantly during a cer- 
tain season of the year in Spain, Southern France and even at times in 
Germany; Petrograd supplies also a large quantity of superior can- 
tharidin. The Spanish fly possesses a fine golden green or bluish color, 
ranges from ^ to | of an inch in length and makes its appearance quite 
suddenly in early summer, when it may be collected by the hundreds, 
clinging principally to such vegetation as the ash, privet and lilac. 
The peculiar hypermetamorphosis of these insects and their larval habits 
give to them some obscurity during their early development and the 
sudden appearance and equally sudden disappearance, owing to short 
adult life, lent the belief that they were migrating forms. 

The collection and preparation of the beetles provides an occupation 
for many persons during the brief period. This process also requires 
special precautions owing to the vesicating properties of the insects. 



50 MEDICAL AND VETERINARY ENTOMOLOGY 

The best quality of cantharidin produced from the pulverized beetles is 
the result of special care in the drying, which must be gradual. Of 
cantharidin, Sollman * (p. 705) says it is the most important local irri- 
tant. " It is a crystalline principle, the anhydrid of cantharidic acid. 
It combines readily with alkalines, forming soluble salts ... it was 
isolated by Robiquet in 1812 from the Spanish fly . . . Lytta vesica- 
toria. . . . Cantharidin is readily absorbed from all surfaces. Even 
when applied to the skin, sufficient may be absorbed to irritate the kid- 
neys, so that fly blisters are contraindicated in nephritis. It is excreted 
mainly by the kidneys. It irritates the gastro-intestinal tract even 
when injected hypodermically so that some must be excreted by this 
channel. . . . Cantharidin penetrates the epidermis quite readily 
and produces violent but superficial irritation. This results in vesica- 
tion. Very small quantities suffice for this purpose, y 1 ^- mg. cantharidin 
. . . will produce blisters on the human skin in the course of a few 
hours." 

As to therapeutic uses the same author states : " Cantharis is the most 
useful of vesicants. . . . The vesicant action of cantharides develops 
rather slowly. (It) is one of the most useful remedies in the treatment 
of baldness. It is used in the form of tincture, very greatly diluted with 
alcohol. For treatment of impotence Cantharis is one of the most 
certain, acting through reflex irritation from the urethral mucous 
membrane. It is, however, quite dangerous, since effective doses are apt 
to set up considerable nephritis." 

C. Thrips 

Order Physopoda 

Thrips and Sneezing. — The introduction of foreign particles into 
the nostrils causes sneezing, this phenomenon being easily induced by 
irritation of the mucous membrane of the nasal chambers. Such a 
paroxysm often follows when a flower is held close to the nose and a 
strong inhalation is made to receive the odor. This strong inhalation 
frequently brings with it small insects which were crawling about on 
the petals of the blossom. Insects habitually inhabiting blossoms are 
most likely to be the guilty ones and of these the commonest minute 
forms are members of the order Physopoda (Thysanoptera) commonly 
called thrips. 

Characteristics. — ■ These rather active insects are characterized by 
their small size (1 to 2 mm.) together with the following unique struc- 
tures, viz. : the foot terminates in a bladder-like organ, whence the 
term Physopoda ; the wings are narrow, but this narrowness is com- 
pensated for by a great development of long, closely set fine hairs along 
the margins of each wing, whence the name Thysanoptera (bristle 

1 Sollman, Torald, 1908. Textbook of Pharmacology, 1070 pp. W. B. 
Saunders Co. 



COCKROACHES — BEETLES — THRIPS 



51 



wings) (Fig. 44a). The mouth parts are also distinctive as already 
explained. 

Systematic. — The order is divided into two subdivisions based on 



the form of ovipositor, 
Terebrantia (Fig. 



tubular in Tubulifera (Fig. 4Ab) ; saw-like 



in 

44c). In the former 
subdivision the ovi- 
positor is cylindrical, 
telescoping in the last 
segment of the abdo- 
men and ending in a 
circlet of bristles ; the 
following commoner 
forms are representa- 
tives of this division : 
Phleothrips xerbasci, 
mullein thrips ; Phleo- 
thrips nigra, clover 
thrips, black in adult 
but bright red in the 
larval stage. The sec- 
ond subdivision, Tere- 
brantia, is represented 
by Euthrips tritici 
Fitch., orange-yellow in color, and found in many blossoms according 
to the time of blossoming (apple blossoms, strawberry blossoms, citrus 
blossoms, and grasses) ; Euthrips striatus Osb. is the grass thrips, also 
yellow, but smaller than Eu. tritici Fitch. ; Euthrips pyri Dan. is the 
pear thrips of the Santa Clara Valley and elsewhere. 




Fig. 44. — Thrips, Order Physopoda. (a) Shows charac- 
teristic bladder feet and bristle wings. X 28. (b) 
Tubular ovipositor of Tubulifera. (c) Saw-like ovi- 
positor of Terebrantia. 



CHAPTER VII 



THE LICE 



A. The Biting Lice 

Order Mallophaga 

Characterization. — This group of parasites is not easily distinguish- 
able from the true sucking lice (the Pediculi) which they closely resemble 
in habit and general form, In mouth parts they are, however, very 
different ; the former are provided with mandibles used in feeding, while 
the latter have a long protrusible sucking proboscis. Furthermore, the 
sucking lice are restricted, as far as known, to mammals, while the 
biting lice inhabit both mammals and birds. The common name 
" bird lice " often applied to these insects is misleading for this reason. 
As in the sucking lice each species is usually restricted to a specific host. 
The body is compressed dorsoventrally, an aid to easy locomotion 

among the hairs or feathers of 
the host. Wings are entirely 
absent, there being no trace of 
these organs present. The sharp 
mandibles are situated in most of 
the species on the ventral surface 
of the head, somewhat posterior 
to the tip, and may be seen under 
the microscope as conspicuous 
black-tipped objects. 

Habits and Life History. — 
The biting lice deposit their eggs 
on the hairs or feathers of the 
host (Fig. 45), to which they are 
securely attached by means of a 
gluey secretion. After fixe to 
eight days incubation the young 
lice emerge and begin their active 
life on the host, which they do 
not leave as a rule except to crawl 
off on to another individual of the same species, ordinarily when in 
close contact. Under severely infested conditions among poultry there 
may possibly be a migration from the host to the roosts and even to 

52 




Fig. 45. — Eggs of biting lice (Mailopnaga) 
on feathers of a bird. (Much enlarged.) 



THE LICE 



53 





Fig. 46. — The biting dog 
louse, Trichodectes latus. 
X35. 



other animals, but the writer's experience has 

been that these infestations are generally due to 

poultry mites which often infest every nook and 

crevice of the henhouse. The biting lice are so 

well adapted to their habitat that they cannot 

well exist away from the host for more than 

several hours. Their food consists of exudations 

from the skin, epidermal scales, bits of feathers 

and hair. Maturity is ordinarily reached in from 

three to four weeks, during which time there are 

apparently about four or five molts, with no 

conspicuous change in form. 

Damage Done. — The damage done by the 

biting lice is largely restricted to poultry, al- 
though some trouble may 
ensue when mammals are 

badly infested. The trouble is largely that of 
irritation due to the crawling about and gnaw- 
ing habits of the parasites. This irritation 
causes the host to become restless, thereby 
affecting its feeding habits and proper diges- 
tion, producing weakness and susceptibility to 
disease. A " lousy " flock of chickens is not a 
profitable investment. 

Systematic. — The biting lice (Mallophaga), 
of which there are over a thousand species, may 
be grouped into two suborders based on the 
following characters, — conspicuous antennae, 
3 or 5 segmented, palpi 
absent, rather sluggish in 
habit, — suborder Ischno- 

cera; or, concealed four-segmented antennse, 

palpi present, active in habit, — suborder Am- 

blycera. 

The suborder Ischnocera is subdivided into 

two families, viz. : Trichodectidae, species in- 
festing mammals, — antennas three-segmented ; 

Philopteridae, inhabiting birds only, — five-seg- 
mented antennas. The suborder Amblycera is 

also subdivided into two families, viz. Gy- 

ropidae, inhabiting mammals only; and Liothe- 

idae, inhabiting birds only. The families may 

be distinguished by the tarsal claws, which are 

distinctly two in number in the latter case and 

modified into clasping organs in the former, one FlG - 48 - — Biting louse of 

i> , t t i«ii the Angora goat, Tricho- 

ot the claws being reduced. dectes hermsi. x 22. 



Fig. 47. — The biting ox 
louse, Trichodectes scala- 
ris. X 26. 




54 



MEDICAL AND VETERINARY ENTOMOLOGY 



Species of Trichodectidae. — Only a few of the commoner species 
need be considered here. The species belonging to this family are 

all small in size 
and belong to the 
genus Trichodectes. 
Trichodectes latus 
Nitzsch (Fig. 46) is 
the biting louse of 
the dog, most nu- 
merous on puppies. 
It is a broad short 
species about 1 mm. 
long, and more than 
half as wide. Tri- 
chodectes subrostratus 
Nitzsch of the cat 
is about the same 
length as T. latus, is 
not so broad and 
has a longer, more 
pointed head. Tri- 
chodectes scalaris 
Nitzsch infests 
cattle. The distinct 
ladder-like markings 
(Fig. 47) of the 
abdomen (present 
though less pronounced) gives rise to the 
is one of the biting 




A biting louse of deer, Trichodectes tibialis 
left; female, right. X 31. 



male, 



also in a few other species 

specific name. Trichodectes parumpilosus Piaget 
lice of the horse, mule and ass. Osborn 1 describes 
this form, viz. : " the head is decidedly rounded 
in front, the antennae inserted well back, so that 
the head forms a full semicircle in front of the base 
of the antennae. The abdomen is more slender 
and tapering than in scalaris. . . . The color is 
much as in the allied species, the head, thorax and 
legs being a bright reddish brown, or chestnut, and 
the abdomen of a dusky yellowish color, with about 
eight transverse dusky bands occupying the central 
or anterior portions of the segments and extending 
from the middle line a little more than halfway to 
the margin. They are hardly as conspicuous as in 
scalaris" Trichodectes climax Nitzsch is fairly 
common on goats, Trichodectes hermsi Kellogg 

1 Osborn, Herbert, 1896. Insects Affecting Domestic Animals, 
of Agr., Division of Entomology, Bull. No. 5, N.S. 302 pp. 




Fig. 50. — A hen louse, 
Goniocotes abdomina- 
lis. X 10. . - - 



U.S.Dept. 



THE LICE 



55 



(Fig. 48) is abundant on the Angora goat, and 
Trichodectes tibialis Piaget (Fig. 49) is exceed- 
ingly abundant on deer. 

Species of Philopteridae. — Infesting chickens 
the following members of this family may be 
considered : Goniocotes hologaster Nitzsch, about 

1 mm. in length, has a squarish head with angu- 
lated temples; Goniocotes abdominalis Piaget 
(Fig. 50), about 3 mm. long, broad with head 
circular in front; Lipeurus variabilis Nitzsch, 

2 mm. in length, a long, very slender whitish 
species. The margins of the 
body are black ; the head is 
large, rounded, and the 
whole appearance sufficiently 
distinct from any other 
species infesting the chicken, 

that there can be 





Fig. 51. — A turkey louse, 
Goniodes stylifer. X 14. 

so tnat tnere can oe no 
difficulty in distinguishing it at a glance. Lipeurus 
heterographus Nitzsch is said to differ from the 
above in having the " head rather narrowed in 
front instead of inflated, and the body is much 
stouter." This species has been taken by Osborn 
from chickens at Ames, Iowa. 

Turkeys are commonly infested with the large 
(3 mm. long) Goniodes stylifer 
Nitzsch (Fig. 51), which has the 
posterior angles of the head ex- 
tended backward into long pro- 
jections or stylets terminating 
in bristles. Another louse found 
on turkeys is Lipeurus polytra- 
pezius Nitzsch, like all members 



Fig. 52.— a duck louse, ° f this species, long and slender, 



Lipeurus squalidus. 
(Redrawn after Os- 
born.) X 19. 



3 to 3^ mm. 



Ducks and geese harbor a 
rather small-sized species of 
louse, Docophorus icterodes Nitzsch (1 mm.), " with 
head curiously expanded and rounded in front, 
darkish red head and thorax with darker bands, and 
a white region in the middle of the abdomen." — 
Kellogg. 1 Another common species infesting ducks 
and geese is Lipeurus squalidus Nitzsch (Fig. 52), 
which, according to Osborn, " is about 4 mm. in 

1 Kellogg, Vernon L., 1905. 
& Company. 




Fig. 53. — A biting 
louse of the guinea 
pig, Gyropus graci- 
lis. (Redrawn after 
Osborn.) X 35. 



American Insects, vii + 674 pp. Henry Holt 



56 



MEDICAL AND VETERINARY ENTOMOLOGY 




length, elongate in form, and of a light yellowish color, with dark border 
to the head, thorax and abdomen. On the latter this border is broken 
into a series of quadrate patches corresponding with the segments." 

Pigeons are affected by several species of biting 
lice, of which Goniocotes compar Nitzsch is quite 
common. It is about 1 mm. in length, described as 
follows : " The head is rounded in front, narrower 
between the antennae, broadest near the posterior 
margin. The thorax is narrower, the abdomen in 
the male broadest near the posterior end and squarish 
behind, in the female more regular and broadest near 
the middle. It is whitish, with a rather broad 
brownish margin, from which prolongations extend 
inward upon the sutures." Another species said to 
be common on pigeons is Goniodes damicornis Nitzsch, 
length 2 mm. ; in color it is brown. Lipeurus baculus 
Nitzsch is a very common form; it is about 2 mm. 
in length and exceedingly slender in conformance with 
the generic character. While the abdomen of this species is dark, the 
head and thorax are reddish brown in color. 






^ 



% 



v 



Fig." 54. — A biting 
louse of the guinea 
pig, Gyropus ovalis. 
(Redrawn after 
Osborn.) X 35. 





Fig. 55. — The common hen louse, Menopon pallidum. Male, left; female, right. X 33. 

The commoner lice of the swan are Docopkorus cygni Denny, about 
1 mm. in length; "in color the head, thorax and legs are bright reddish 
brown while the abdomen is white in the center and dark brown at the 



THE LICE 



57 



sides, the brown occupying hard plate-like portions at the side of each 
segment ; " and the extremely large and common Omithobius bucephalus 
Piaget (4 mm. long). The latter is conspicuous because of its size, 
although the body is white and quite transparent. 

Family Gyropidae. — The members of this family are restricted to 
mammals. The genus Gyropus is a typical representative, of which 
G. gracilis Nitzsch (Fig. 53), a long slender form, is easily distinguish- 
able from G. ovalis Nitzsch (Fig. 54) by comparing the figures ; both 
species are found on the guinea pig. 

Family Liotheidae. — The commonest representative of this family 
is the widely known chicken louse, Menopon pallidum Nitzsch (Fig. 55). 
This species is the most prevalent of all the hen 
lice, is an active runner, light yellow in color 
and about 1^ to 2 mm. in length. Another 
• member of this family, also infesting chickens, 
is Menopon biseriatum Piaget (Fig. 56) , a some- 
what larger species, and considerably less com- 
mon. The head and anus of young chicks and 
turkeys seem to be frequently attacked by this 
species. Trinoton luridum Nitzsch of ducks is 
a large species measuring 4 to 5 mm. in length. 
Trinoton lituratum Nitzsch of the goose is 
smaller than the former, considerably lighter 
and without the dark markings. 

To Control Poultry Lice. — The very fact 
that poultry bathe in dust whenever available 
indicates a potent means of controlling the bird 
lice. In the erection of a modern poultry house 
the dust bath should be carefully provided for. 
Special boxes, broad and deep enough so that there will be room for 
several birds at a time, should be partly filled with fine road dust or 
ashes with the addition of a quantity of tobacco dust in the proportion 
of about six parts of the former to one of the latter. It is quite de- 
sirable to add a few handfuls of sulphur. The finer the dust the better, 
since the principle on which its use is based is that of suffocation, i.e. the 
dust particles enter and clog up the breathing pores of the lice. It is 
quite probable that the agitation caused by the dust and the " wallow- 
ing " of the bird dislodges many of the lice and they are lost in the 
shuffle. A very good louse powder for dusting birds by hand is pre- 
pared by mixing gasoline, 3 parts, and carbolic acid (about 90 per cent 
pure), 1 part, and stir into this mixture enough plaster of paris to take 
up the moisture. When preparing this mixture, it must be borne in 
mind that the gasoline is highly inflammable and that the carbolic acid 
is poisonous and injurious to the skin. Pyrethrum powder or buhach 
(fresh) applied to the hen directly by means of a duster is also a good 
remedy. A small handful of naphthaline flakes in each nest is very 




Fig. 56. — The head louse 
(Menopon biseriatum) of 
young fowls. X 16. 



58 



MEDICAL AND VETERINARY ENTOMOLOGY 



useful. Dipping chickens in a 2 per cent solution of chlorine is recom- 
mended by some. 

The biting lice of mammals may be combated as described below 
for the Pediculids. 

B. The Sucking Lice 



Order Hemiptera, Suborder Parasita. Family Pediculidce 

Characterization. — With the characteristics of the biting lice well 
in mind there will be little difficulty in recognizing the sucking lice. 
The members of this group are suctorial, blood sucking, and restricted 
to mammals. The proboscis consists of a long fleshy extensile tube 
inclosing three slender stylets. The mouth parts are of the Hemip- 
teron type except that the proboscis is not jointed. All the species are 
wingless, body compressed, antennae five jointed, and tarsi are provided 
with strong claws adapted to hold the parasite firmly to the hairs of 
its host. 

Pediculosis. — An infestation of lice is ordinarily termed Pedicu- 
losis, whether it involves man or beast ; the term Phthiriasis denotes 
infestation by the pubic louse in particular. Pediculosis in animals 
may be indicated by the tendency to scratch and an 
effort to relieve the irritation by rubbing on rough 
objects, such as fences, posts, etc. These symptoms 
may, of course, indicate the presence of fleas or itch 
mites, but lousy animals usually have a rough, bristly 
coat, the eyes being " wild " in appearance, the 
body often emaciated. 

Life History. — The barrel-shaped eggs or " nits " 
are deposited on the hairs of the host (Fig. 57) and 
are glued fast by means of a sticky secretion. The 
period of incubation covers commonly from five to six 
days, the young insect on emerging having the general 
appearance of the adult except for size. Maturity is 
reached in most cases in from three to four weeks, 
which accounts for the rapid multiplication of these 
parasites. The dissemination of lice from one host 
to another is brought about by close association or 
by the indiscriminate use of toilet articles, clothing, 
currycombs, combs, brushes, etc. 

Systematic. — All species of sucking lice which inhabit domesticated 
mammals belong to the genus Hsematopinus. As is true in other genera, 
the legs are short and thick ; in consequence their movements are very 
sluggish, and migration from host to host is not easily accomplished, 
except in certain species, such as the body lice of man, which are rather 
active. The genus Pediculus is restricted to man and the anthropoid 




Fig. 57. — Nits or 
eggs of a sucking 
louse attached to 
the hair of the 
host. One of the 
eggs has hatched. 
X 10. 



THE LICE 



59 




Fig. 58. — Life history of the human head 
louse, Pediculus capitis, a. egg ; b. larva ; 
c. male ; d. female. x 10. 



apes. There is comparatively little structural difference between its 
members. The genus Phthirius is readily distinguishable from all other 
genera by its distinctly crablike ap- 
pearance, broad body and strong 
clasping appendages. 

Species affecting Man. — The 
three species of Pediculids infest- 
ing man are cosmopolitan and ob- 
jects of great antiquity. The head 
louse, Pediculus capitis DeG. (Fig. 
58), is about 3 mm. in length in 
the female and about 2 mm. in the 
male, varying from a light leaden 
color to nearly black. This dif- 
ference in color is said to corre- 
spond to the color of the human 
host, also with the color of the 
hair in Caucasians. Murray l says, 
" Those of the West African and 
Australian are nearly black ; those 
of the Hindu, dark and smoky; 
those of the Africander and Hottentot, orange; those of the Chinese 
and Japanese, yellowish brown ; of the Indians of the Andes, dark 

brown ; of the Digger Indians of 
California, dusky olive, and those 
of the North American Indian 
near the Eskimo, paler approach- 
ing to the light color of the para- 
sites of the European." The 
eggs of the head louse are quite 
conspicuous, pear-shaped objects, 
usually attached near the base of 
the hair at the neck and back of 
the ears. Fifty is given by some 
writers as the number of eggs 
deposited by the female, and the 
great rapidity of reproduction be- 
comes evident when it is known 
that the young female requires 
only about three weeks to reach 
maturity. In bad cases of pe- 
diculosis the hair of the head may 
literally become a mass of nits 

Fig. 59. — Human body louse, Pediculus vesti- Qri J •, 



s 




( 


/IPs >/ Lin 




- 


»'*•''*»* 


§£fc 




I 








> 

1 

r 












ajj^ 



mcnti. 



X 15. 



1 Murray, Andrew, 1860. On the pedieuli infesting the different races of 
man. Trans. Roy. Soc. Edinb., T. 22, p. 3, p. 567 (cited by Osborn). 



60 



MEDICAL AND VETERINARY ENTOMOLOGY 







'-H'~ 
















^gSf^P': 





Fig. 60. 



The pubic louse, Phthirius ingui- 
nalis. X 23. 



Individuals who have had experience with the several forms of 
Pediculids say that the head louse does not produce the great discom- 
fort that is caused by the body louse, Pediculus vestimenti Leach (Fig. 
59). In size the body louse is somewhat larger than the head louse, 

ranging from 3 to 4 mm. in 
length. Size is not a good cri- 
terion for the separation of the 
two closely resembling species 
because of intergradation in the 
younger stages. However, by 
comparing the two species it 
will be seen that the antennae 
of the body louse are relatively 
longer and more slender and 
that the abdomen is broadly 
attached to the thorax. This 
species infests the clothing of 
human beings, particularly that 
worn next to the body, where 
the eggs are deposited. Careful 
observations on the life history 
of this parasite were made by 
Warburton (see Nuttall 1 ), who found that the female laid 124 eggs 
during the course of twenty-five days, and hatched in eight days under 
favorable conditions. The adult stage was reached on the thirteenth 
day after three molts, which occurred about every fourth day. Adults 
entered into copulation five days 
after the last ecdysis or molt. The 
adults reared by Warburton lived 
about three weeks after the final 
molt, and the " egg to egg " period 
was reckoned at about twenty-four 
days. Irritation is caused by suck- 
ing blood and by scratching with 
their claws while crawling about on 
the skin. The grayish color which 
is characteristic of this species gives 
rise to the significant term " gray- 
back." The " gray-back " is usually 
the unwelcome associate of camp 
laborers, soldiers and rangers, and is commonly looked upon as a part 
of the initiatory features of such life. 

If there is any possibility of degree in the matter, the most dis- 
gusting of all lice infesting human beings is the pubic or c^ab louse, 

1 Nuttall, G. H. F., 1913. The Herter Lectures I. Spirochetosis. Para- 
sitology, Vol. 5, No. 4, pp. 271-272. 




Fig. 61. — Hog louse, Hcematopinus (urius) 
suis. X 7. 



THE LICE 



61 




fjr 



Fig. 62. — The 
short-nosed ox 
louse, Hcema- 
topinus eury- 
sternus. (Re- 
drawn after 
Osborn.) X22. 



Phthirius inguinalis Leach (Fig. 60), which infests the pubic region 
particularly and the armpits, rarely other parts. The ease with which 
this form is transmitted accounts for the astonishing abundance and 
frequent occurrence of these parasites on men in various stations in 
life. Its identity cannot be mistaken if the appended 
figure is taken into account. It measures from 1 to 1.5 
mm. in length and is nearly as broad as long. The eggs, 
not usually more than a dozen per female, are attached 
to the coarse hairs of the region infested. The incuba- 
tion period lasts from five to six days and full growth 
is reached in about three weeks. 

Species affecting Domesticated Animals. — The prin- 
cipal species of pediculi infesting the domesticated ani- 
mals belong to the genus Hsematopinus. Each of these 
species inhabits a specific host, so that, in all but acci- 
dental cases, the specific name may be known when the 
parasite is taken on its host, with only a good hand lens 
as an aid to identification. Hcematopinus suis Linn. 
(Fig. 61) of the hog is the largest representative of the 
genus, measuring as much as 5 to 6 mm. in length. It is a cosmopoli- 
tan species, often infesting the host in great numbers. It seems evi- 
dent, from general observations, that the presence of these parasites 
when numerous affects swine quite seriously. Next to cholera this 
louse is said to be the hog's worst enemy. The head of the hog louse 
is long, and together with the thorax and abdomen is 
provided with a conspicuous dark border. H. (asini 
Linn.) macrocephalus Burin, of the horse is smaller (2.5 
to 3 mm.), otherwise similar in form, except that the 
head is relatively longer and more robust. Cattle may 
be infested with one of two species, H. eurysternus 
Nitzsch, the short-nosed ox louse, or H. vituli Linn., the 
long-nosed ox louse. The former is somewhat the larger 
(1.5 mm. to 2 mm.), broader in proportion and short 
nosed (Figs. 62-63). The long-nosed ox louse is said 
to infest the neck and shoulders in preference to other 
parts. H. yedalis Osb. is the sheep foot louse, said by 
Osborn to occur only on the legs and feet below where 
the long wool is found, and particularly in the region 
of the dew claws, where the eggs appear to be most 
commonly deposited. In shape it resembles the long- 
nosed ox louse, but is more slender. 

Although other observers have found the sucking 
dog louse, H. piliferus Burm., less common than the biting dog louse, 
the writer has found this species quite as common in California if not 
relatively more abundant. The adults are about 2 mm. in length ; 
the antennae are short and heavy, as are the legs, while the hairy ab- 
domen is oval and usually apparently swollen. 




Fig. 63. — The 
long-nosed ox 
louse, Hcemato- 
pinus vituli. 
(Redrawn after 
Osborn.) X 30. 



62 MEDICAL AND VETERINARY ENTOMOLOGY 

Other Species of Haematopinus. — Experiments with rodent lice 
as transmitters of trypanosomes have brought several of these species 
into prominence, notably Hcematopinus spinulosus Burm. of the rat. 
It is light yellow in color, the head projecting very little in front of the 
antennas, and the thorax is very short. H. acanthopus Burm. is the 
sucking louse of the field mouse, while H. hesperomydis Osb. occurs on 
the white-footed mouse. The ground squirrel harbors a species known 
as H. suturalis Osb., described by Osborn, viz. " This species is particu- 
larly well marked by the general form of the body and especially by the 
conspicuous transverse suture back of the antennas. It differs further 
from most of the species in the genus in having both the anterior and 
middle legs slender and of nearly the same size, while the posterior legs 
alone are especially modified as clasping organs." 

Relation to Disease. — Lousiness may correctly be designated as 
a disease and is technically termed Pediculosis or Phthiriasis. This 
applies equally well to either the biting or sucking lice. While the 
presence of lice on the body of an animal may not result in serious conse- 
quences, nor even in much discomfort, an abundance of these parasites 
naturally results in a weakened condition, predisposing the host to other 
diseases through loss of blood (when infested with sucking lice) and 
general irritation resulting in poor digestion. Intense irritation, 
pruritus, on the trunk of the body in human beings is often the result 
of body lice. Furthermore, it is quite certain that infection may be 
transmitted from animal to animal (of the same species) by lice, either 
upon feet and mouth parts, as the bee carries pollen, e.g. impetigo, or 
within their bodies, as explained under spirochetosis. 

Impetigo. — In the human such diseases as Impetigo and Favus may 
be transmitted by the pediculi. Tropical impetigo {Pemphigus contagi- 
osus) is said to be caused by Diplococcus pemphigi contagiosi Wherry, 
while favus is traceable to a fungus variously classified, probably best 
known as Achorion schoenleini. The following experiments cited from 
Nuttall, 1 bear evidence to the transmission of impetigo : "Dewevre (1892) 
claims that pediculi disseminate impetigo. He removed ten pediculi 
from a child suffering from impetigo and placed them on a healthy 
infant, which a few days later developed impetigo. The experiment 
was repeated several times with the same results. In a second series 
of experiments, he took scrapings from under the nails of children that had 
impetigo, and placing them on artificially scratched places, reproduced 
the disease. Lastly he took pediculi from a child that was not affected 
with impetigo and placed them on a child that had the disease ; removing 
them after twenty minutes, he replaced them on a healthy child. The 
latter acquired the disease, as did fifty per cent of the children so experi- 
mented with. He claims the specific microorganism adheres to the 
front legs especially, also to the hairs of the insect, and the latter 
carries them as bees do pollen. In the last set of experiments, he only 
i Nuttall, G. H. F., 1899 (loc. tit.). 



THE LICE 



63 



r~ 



% 



\- 



\ 



mm 



S 






Fig. 64. — Smear preparation show- 
ing Treponema pallidum of syph- 
ilis. (Greatly enlarged.) 



allowed the pediculi to remain half an hour on the healthy head, but 
this was sufficient to produce infection." The above typical example 
also illustrates the methods used to secure the experimental evidence of 
transmission. 

Spirochetosis. — An infection of spirochetes is known as spiro- 
chetosis. The spirochsetse are protozoa belonging to the class Zoomasti- 
gophora (Flagellata), order Spirochsetida. 
They consist of undulated filamentous 
bodies, in some of which there is said to 
be present a narrow membrane extend- 
ing from end to end of the body. In 
the genus Treponema, e.g. Treponema 
pallidum Schaudinn (Fig. 64) of syphilis, 
the membrane is absent and the body is 
strongly spiral ; in the genus Spirochseta, 
e.g. Spirochceta novyi (Shellack), the body 
is wavy or undulatory (Fig. 65). 

Both man and beast are affected by 
Spirochetosis, but in the former the term 
relapsing fever is ordinarily applied. The 
relapsing fevers are characterized by 
fevers sudden in appearance and rather sudden in subsidence, with 
relapses at irregular and indefinite intervals. The mortality is given 
at about 5 per cent. Relapsing fever is most likely to be confused with 
malaria but for the characteristics above mentioned and the presence 
of spirochetes in greater or less number in the blood of the patient. 

The African relapsing fever, traceable to 
Spirochceta duttoni (Novy and Knapp), is 
transmitted by ticks; while the European 
form, traceable to Spirochceta recur rentis 
(Lebert), the American form (Spirochceta 
novyi Shellack) and the Indian form (Spi- 
rochceta carteri Mackie) are transmitted by 
the pediculi, as later described. 

The first important evidence to the effect 
that lice may be concerned in the trans- 
mission of relapsing fever was advanced by 
Mackie 1 in India in 1907, who records an 
outbreak of the disease among school chil- 
dren, in which 137 out of 170 boys and 35 
out of 114 girls were attacked. Twenty-four per cent of the lice re- 
moved from the boys contained spirochetes, while only 3 per cent of 
the lice removed from the girls were infected. As the parasites in- 
creased in abundance among the girls, so also did the epidemic increase, 

1 Mackie, F. P., 1907. The part played by Pediculus corporis in the trans- 
mission of relapsing fever. British Med. Journ. 2 1907, p. 1706. 




Fig. 65. — Spirochata novyi in 
a blood smear. (Greatly en- 
larged.) 



64 MEDICAL AND VETERINARY ENTOMOLOGY 

and conversely as the parasites became less abundant among the boys, 
so also did the epidemic decrease. The spirochetes were observed to 
multiply in the intestine of the lice and were found to be present in 
the ovaries, testes and Malpighian tubules. Mackie concluded that 
infection might be spread by the lice by regurgitating the spirochetes 
into the wound produced by the bite. 

Later (1912) Nicolle, Blaizot and Conseil 1 failed to transmit the 
spirochetes through the bites of infected lice, and found that the only 
reliable successful experiments involved the injection or subcutaneous 
inoculation of an extract of infected lice. 

Based on experiments in which men and monkeys were exposed to 
hundreds of bites, Nicolle and his colleagues came to the conclusion that 
transmission is brought about by the introduction of spirochetes re- 
ceived under the finger nails and on the finger tips from crushed parasites, 
which are inoculated into excoriated skin in scratching. They also 
found that the spirochetes disappear and later reappear, only a few 
remaining in the insect's intestine up to five or six hours after infection, 
and none after twenty-four hours, but reappear in the insect in from 
eight to twelve days and are then present in the general body cavity, 
none being found in the alimentary canal. It was also found that the 
spirochetes are transmitted to the offspring of infected lice. 

The incubation period in the human is said to be from seven to ten 
days. 

Typhus Fever. — Typhus fever, known also as tarbardillo (Mexico), 
Brill's disease (United States), jail fever or war fever, is a disease of 
ancient origin and wide distribution. The disease is characterized by 
a high fever, backache, headache, bronchial disturbances, congested face 
(designated also as a " besotted expression "), brick-red mottled eruption 
which later spreads, becoming brownish irregular blotches. This 
spotting led to the belief that tarbardillo of Mexico was identical 
with spotted fever of Montana, a fact proved untrue by Ricketts, who 
lost his life by typhus fever during the course of his investigation. 
Experiments and observations by Nicolle and Ricketts and Wilder 2 
indicate that the bedbug and the flea are not instruments of trans- 
mission. That the body louse (Pediculus vestimenti) is the most impor- 
tant, if not sole agent, in the transmission of typhus fever has been proved 
by Nicolle et al. 3 (1909, working in Tunis) and Ricketts and Wilder 4 

1 Nicolle, C. N., Blaizot, L., and Conseil, F., 1913. Ann. Inst. Pasteur, 
March 25, 1913, pp. 204-225. 

2 Ricketts, H. T., and Wilder, R. N., 1910. Further investigations regard- 
ing the etiology of tarbardillo, Mexican typhus fever. Journ. Amer. Med. Assoc, 
Vol. 55, No. 4, pp. 309-311. 

3 Nicolle, Charles, Comte, C, et Conseil, E., 1909. Transmission experi- 
mentale du typhus exanthimatique par le pou du corps. Paris Acad. Sc. 
Comptes Rendus, T. 149, pp. 486-489. 

4 Rickets, H. T., and Wilder, R. M., 1910. The transmission of the typhus 
fever of Mexico (tarbardillo) by means of the louse (Pediculus vestimenti). 
Journ. Amer. Med. Assoc, Vol. 54, No. 16, pp. 1304-1307. 



THE LICE 65 

(1910, working in Mexico). The latter found that Macacus rhesus can 
be infected with tarbardillo (Mexican typhus) invariably by the in- 
jection of virulent blood from man taken on the eighth to tenth day 
of fever, that the monkey may pass through an attack of typhus so 
mild that it cannot be recognized clinically and that vaccination results. 
Typhus was transmitted to the monkey by the bite of the louse in two 
experiments, the lice in one instance deriving their infection from man 
and in another from the monkey. Another monkey was infected 
through the introduction of the feces and abdominal contents of infected 
lice into small incisions. The causative microorganism of typhus is 
claimed by Plotz to be a small Gram positive, pleomorphic bacillus. 

The incubation period in the human is from ten to twelve days. 
The duration of the disease is said to be about twelve days in children, in 
which it is usually comparatively mild, to twenty-one to twenty-four days 
in adults. The mortality is said to range from 15 per cent to 30 per cent, 
but may be as high as 50 per cent to 75 per cent under war conditions. 

Rat Trypanosomiasis. — A relatively common and apparently non- 
pathogenic protozoan parasite of the rat is Trypanosoma leicisi Kent. 
Various observers, among them Brumpt and Minchin and Thomson, 
have determined that this trypanosome is transmitted by the rat louse, 
H&matopinus spinulosus, in which host the protozoon undergoes certain 
developmental changes. Other insect hosts of the trypanosome are 
known, among them the rat flea, Ceratophyllus fasciatus. 

Relation to Taeniasis. — Dipylidium caninum Linn. (Taenia cucu- 
merina), the double-pored dog tapeworm, is a common parasite of the 
dog and is occasionally found in humans, especially children. It meas- 
ures from ten to fourteen inches in length, has long seedlike pro- 
glottides and an armored scolex, and has as its larval host the biting 
dog louse, Trichodectes latus. 1 The larva or bladder worm, known as 
Cysticercus trichodectes, has been experimentally produced in the louse 
by placing ripe crushed proglottides of the tapeworm on the skin of a 
dog infested with lice. 

As has already been explained, the biting lice subsist on epidermal 
scales, skin exudations and other matter on the skin of the animal. 
This habit makes it comparatively easy for the louse to become infected 
through eggs in the kennel in which the dog lies. The dog, on the other 
hand readily infects himself by devouring the lice which irritate his skin. 

Persons, particularly children, while fondling louse-infested dogs 
may easily become infected by accidentally swallowing lice which con- 
tain bladder worms. This is more readily accomplished if the person 
is eating at the time. 

How Lice are Disseminated. — The most effective means for the 
distribution of lice on humans is the indiscriminate use of toilet articles, 
garments and bedding ; also close association. The mere presence of lice 

1 Occurs also in the dog flea, Ctenocephalus canis, and in the human flea, 
Pulex irritans. 



66 MEDICAL AND VETERINARY ENTOMOLOGY 

does not invariably indicate uncleanly habits, but the continued presence 
of these parasites is inexcusable. Cases have come under the observa- 
tion of the writer in which several members of a highly respectable 
family were sadly infested with the head louse, to their great dismay. 
Members of this family were greatly alarmed, believing themselves 
disgraced for all time. The infestation was thus explained. It was 
found that a maid employed by the family had previously been engaged 
by another family whose children became infested in school, as may 
happen. In caring for the children the maid in turn became infested 
and shortly thereafter sought another position, which was found with 
the family in question. By indiscreet use of combs and brushes a 
general infestation was inevitable. 

Domesticated animals may have lice communicated to them by 
close association, especially in the winter time, and by infected curry 
combs, blankets and similar articles, also by rubbing on stalls, fences, 
etc. against which infested animals have previously rubbed themselves. 

Treatment. — Personal cleanliness is by far the best method to 
prevent lice from gaining a foothold; however, the exception has al- 
ready been indicated. The mere use of water is ineffective in destroying 
vermin present in the hair, and the " nits " are even more difficult to 
destroy. In the case of the body louse, a clean body would not prevent 
reinfestation if the same underclothing are put on in the absence of a 
change, which often occurs where men are necessarily far removed from 
civilization or are under accidental conditions. 

To free the head of lice a fine-tooth comb dipped in any hair pomade 
containing oil may be used. Dipping the comb in ordinary kerosene 
before applying to the head is a method frequently employed with good 
results. Several families in which this method has been followed under 
the writer's observation were completely freed of the parasites in that 
manner, with at least no apparent injury to the hair, an objection some- 
times raised. The oil coming in contact with the lice kills them, but 
the eggs or nits cannot be destroyed so well: therefore the combing 
process must be repeated three times at intervals of one week in order 
to destroy the newly hatched lice and thus prevent fresh propagation. 
Care should be exercised in removing the parasites, so that further 
dissemination does not occur. A good method is to use a black oil- 
cloth or slate upon which the combings are placed and the parasites 
certainly destroyed by an application of kerosene. The whitish para- 
sites can readily be seen on the black background and none need escape. 
Washing the head in a 2 per cent solution of creolin is also effective if 
repeated as above. Winding the head in long towels wet with tincture of 
larkspur (DelphiniunO, 10 per cent, is strongly recommended by many. 

The heads of children with long hair may be treated success- 
fully in the following manner, as described by Whitfield in the 
Lancet (Dec. 14, 1912). The child is placed on its back in a bed, with 
the head hanging over the edge, so that the hair falls in a basin resting 



THE LICE 67 

on a chair. The solution to be used (the author recommends Phenol 
12 grams and water 500 grams) is poured over the hair and carefully 
washed back and forth for a period of ten minutes until the hair is well 
soaked, particularly back of the ears and the nape of the neck. After- 
wards the hair is drained, not wrung out, however, and is then put up 
with a towel or flannel cloth in turban fashion. After an hour the hair 
may be washed out or simply left to dry, when it will be found that all 
the pediculi as well as the ova have been destroyed. 

Body lice can only be controlled by treating the clothing and bedding 
of the person infested. A favorable abode is provided by the folds and 
hems of undergarments where the eggs are deposited and where a 
lively existence is manifested. Consequently the necessity for a com- 
plete stripping off of all wearing apparel to the smallest detail becomes 
apparent. All garments should then be at once subjected to a baking, 
steaming or fumigating process; the undergarments may be boiled. 
Soaking all garments in gasoline or benzine is also recommended. 
It is suggested that this is the simplest process as it kills all the adults 
at once, and if it can be repeated ai short intervals, the clothing can 
be worn in the period between treatments. The extreme irritation 
caused by body lice may be relieved by the application of a lotion 
of one half ounce of borax to a pint of water. 

In dealing with lice under typhus fever conditions the greatest care 
must be exercised owing to the minuteness of the parasites and the 
great danger from infection. The patient must be completely stripped 
in a special room, placing his garments at once in a vessel and covering 
them immediately with benzine or gasoline. The face and head 
must be shaved and the hair burned at once. All instruments must 
be carefully sterilized. 

The liberal use of kerosene on floors and beneath cots is strongly 
urged. Rubbing the body with kerosene acts as a good preventive; 
the use of flowers of sulphur has also been recommended. 

The pubic louse, easily disseminated, is also easily eradicated be- 
cause of its local occurrence in both the adult stage and the egg. How- 
ever, notwithstanding the ease of locating them, they are extremely 
tenacious, and repeated applications of the remedy must be resorted to. 
Mercurial ointment (blue ointment) applied as a salve to the parts 
affected is commonly used. The proportions recommended are two 
parts of mercurial ointment and one part petrolatum. The use of 
mercurial ointment directly after a bath may produce bad results, and 
furthermore the salve is not to be strongly rubbed in. Tincture of 
larkspur (Delphinium) 10 per cent is recommended or also 10 per cent 
solution of fishberry and alcohol or just plain kerosene. All treatments 
must be repeated at least three times at intervals of about one week 
in order to destroy larva? newly emerging from eggs not attacked by 
the chemicals. An application of vinegar makes the eggs more suscept- 
ible to the treatment. 



68 MEDICAL AND VETERINARY ENTOMOLOGY 

Control on Animals. — When domesticated animals are lousy, their 
quarters must be thoroughly cleaned and disinfected, together with 
currycombs and similar articles. The latter may be dipped in kerosene 
or crude oil. Cattle, sheep and hogs may be dipped, sprayed or hand 
dressed with tobacco decoctions. Owing to differences in nicotine 
content tobacco dips must be used as specifically directed. Creolin, 
2 per cent for dogs, cats, monkeys, and 4 per cent for hogs is useful ; 
kerosene emulsion (10 per cent for hogs), tincture of larkspur 40 per 
cent, or other remedies such as Kreso, Chloronaphtholeum, etc., as spe- 
cifically directed. Horses, of course, should not be dipped, but may be 
treated with creolin 2 per cent or kerosene emulsion 10 per cent, or 
other remedies above mentioned by local applications with rub rags or 
currycomb. Kerosene in any form should not be applied to animals 
in the hot sunshine. All treatments for lice must be repeated at least 
three times at intervals of about a week to ten days in order to destroy 
the young lice emerging from eggs not destroyed by chemicals. It is 
advisable to add creolin to hog wallows from time to time, a measure 
which proves very useful in keeping the animals comparatively free from 
lice. 

Fumigation for lice is seldom practiced, because of the special equip- 
ment necessary and time required for the operation. Osborn has 
successfully used fumigants in the control of the short-nosed ox louse. 
In his experiments the animal was placed in a tight box stall, one end 
having a close-fitting door to admit the largest animal to be treated, 
the opposite end a stanchion in which the animal is fastened. An 
opening at the stanchion end of the stall is made for the animal's head 
to protrude, and is surrounded by a sack-like covering open at both 
ends, the inner end nailed to the opening and the other made to fit 
tightly around the head just in front of the horns, thus exposing the 
eyes and nose to the air. The fumigating substance is introduced 
into the stall through an opening at the side near the bottom. Osborn 
used tobacco, which was placed on a wire screen over a tin trough con- 
taining alcohol. He states that it should, however, be burned with 
coals or by using a small quantity of kerosene. One or two ounces of 
tobacco and an exposure of twenty to thirty minutes was found effective. 
He also adds that pyrethrum might even be better than tobacco. The 
time of exposure necessary will vary. 









CHAPTER VIII 
BEDBUGS AND CONE-NOSES 

A. The Bedbugs 
Order Hemiptera, Family Cimicidce 

Characterization. — Members of the family Cimicidae (Acanthiidae) 
are extremely flattened in form, fitted to crawl in narrow crevices. As 
adults they are reddish brown in color and wingless but for the merest 
pads and are possessed of a characteristic pungent odor which when 
once noted will be easily recognized thereafter. The mouth parts 
of this family are of the typical Hemipteron type ; they are three-seg- 
mented and inclose long slender stylets. The Aradidae, or flat bugs, 
in their younger stages are often mistaken for Cimicidse. The bed- 
bugs are normally intermittent parasites, but may undergo long periods 
of starvation, at least one year. 

Systematic. — The family Cimicidae belongs to the Order Hemiptera, 
which is subdivided into three divisions or suborders : (1) Heteroptera, 
in which the forward pair of wings, when present, are thick and leathery 
(coriaceous) proximally, and membranous distally ; the mouth parts 
are free and the long axis of the head forms a straight line with the 
body, e.g. Cone-noses (Ruduviidae), Squash bugs (Coreidae) and Bed- 
bugs (Cimicidse) ; (2) Homoptera, in which the wing covers, when 
present, are membranous throughout and the mouth parts may or 
may not be fused to the thorax, while the long axis of the head forms 
a right angle with the body, e.g. Cicadas (Cicadidse), Leaf hoppers 
(Membracidae) and Plant lice (Aphididae) ; (3) Parasita, which includes 
the sucking lice (Pediculidae) already considered. 

The three principal genera of the family Cimicidse 1 are (1) Cimex, 
in which the rostrum is short, reaching about to the anterior coxae ; 
body covered with short hairs, only the lateral sides of pronotum and 
elytra fringed with longer hairs ; antennae with the third and fourth 
joints very much thinner than the first and second and capillary ; (2) 
(Eciacus, in which the body is clothed with long silky hairs ; third and 
fourth joints of the antennae only a little thinner than the first and second 
and filiform ; (3) Haematosiphon, in which the rostrum is long, reaching 
to the posterior coxae. 

The genus Cimex, among others, is represented by the common bed- 

1 Horvath, G., 1912. Revision of the American Cimicidse. Annales Musei 
Nationalis Hungarici, Vol. X, pp. 257-262. 

69 



70 



MEDICAL AND VETERINARY ENTOMOLOGY 



bug, C. lectularius Linn.; it has the body covered with short hairs; 
the second joint of the antennae is shorter than the third. C. pilosellus 
Horv. is a parasite of bats (C. pipistrelli Jenyns is European) ; it has 
the body covered with longer hairs, and the second and third antennal 
joints equal in length. C. hemipterus Fabr.( = C. rotundatus Patton = 
C. macrocephalus Kirk.) is a parasite of man and poultry as well ; it 
occurs in Africa, Asia, South America and Jamaica. In this species 
the lateral sides of the pronotum are dilated, not reflexed, fringed 
with less dense and nearly straight hairs, elytra with the apical 
margin distinctly rounded (Horvath). 




Fig. 



66. — The common bedbug, Cimex lectularius. Male, left ; female, right. Also shows 
piercing stylets exposed. X 10. 



The genus (Eciacus is represented by the European barn swallow bag, 
0. hirundinus Jenyns, and 0. mcarius Horv., the corresponding 
American species. 

Hcematosiphon inodorus Duges is, the only known species of this 
genus, and infests poultry in Mexico and southwestern United States. 
The generic characters already referred to serve to distinguish this 
species. 

The Common Bedbug. — The common adult bedbug, Cimex 
lectularius Linn. (Fig. 66), measures from 4 to 5 mm. in length, 3 mm. in 
breadth, is obovate in form and much flattened. The adult is reddish 
brown in color, though the young insects are yellowish white. Among 
the local names applied to these insects are " chinches," " chintzes," 
" red coats," " mahogany flats," " wall louse," " bedbugs " or simply 
" bugs." 

Bedbugs, like the lice, have been the constant companions of man 



BEDBUGS AND CONE-NOSES 71 

for centuries, — the earliest writings on Natural History (Pliny and 
Aristotle) make mention of them. 

Habits and Life History. — Bedbugs are nocturnal in their feeding 
habits, hiding in crevices during the day. At night they are very active, 
crawling out of their hiding places often to travel considerable distances 
to attack their victims. This is especially true where iron bedsteads 
are used which do not provide convenient hiding places for the bugs. 
Ordinarily where the old-fashioned wooden bedsteads are used the 
bugs stay closer to their point of attack. They are gregarious, hence 
often great assemblages may be found in some convenient crevice. In 
such situations the eggs are usually deposited. 

The females deposit from 75 to 200 rather large yellowish white eggs 
easily visible to the naked eye. As in many Hemiptera, often only 
very few eggs are deposited at a time and oviposition occurs at intervals 
during a period of from two to three months. The period of oviposition 
is apparently limited to the spring and summer months, notwithstanding 
the fact that the insects are commonly favored by warm rooms during 
the winter. The eggs are whitish in color and distinctly reticulated. 
The young, which have the general form of the adults (therefore simple 
in their metamorphosis), hatch in from five to twelve days, influenced 
by temperature, however, as is their later growth. Thus the results of 
experiments and observations of writers differ greatly with regard to 
the life history. The time required for development from the egg to 
maturity is given at from forty-five days to eleven months and there 
may be two or more generations. Ordinarily eight to ten weeks are 
required to reach maturity. The presence or absence of food influences 
this period greatly. Marlatt 1 has shown that bedbugs molt five times 
and that the minute wing pads make their appearance with the last 
molt. He also found that ordinarily but one meal is taken between 
each molt and one before egg deposition and that an average period of 
eight days is required between moltings. 

Methods of Distribution. — Bedbugs, like lice or any other organism, 
cannot originate spontaneously in filth as is believed by many; they 
must be introduced in some manner, either in the form of eggs, young 
or adults. Thus the introduction of one impregnated female might 
furnish the nucleus for a well-developed colony of bedbugs inside of a 
few months. Hence the best regulated household is not exempt from 
invasion, though cleanliness is the best preventive against the multipli- 
cation of any household pest. 

Public conveyances are commonly means for the dissemination of 
bedbugs. As Smith 2 has well said, " I have seen them in railroad 
cars, trolleys, boats, omnibuses and carriages, and have noted them 

1 Marlatt, C. L., 1902. The Bedbug. Circ. No. 47, Second Series, U. S. 
Dept. of Agric, Div. of Entomology. 

2 Smith, John B., 1909. Our Insect Friends and Enemies. J. B. Lippin- 
cott Co., 314 pp. 



72 MEDICAL AND VETERINARY ENTOMOLOGY 

crawling on the clothing of well-dressed fellow passengers who probably 
did not bring them in." Furthermore, migration from house to house 
by way of water pipes, walls and the like is not at all unlikely when in- 
fested houses are vacated and the food supply is cut off. They are also 
easily carried in clothing, traveling bags, suit cases, etc. 

Bedbug Bites. — Persons " bitten " by bedbugs are differently 
affected ; in some the bite produces marked swellings and considerable 
irritation, while in others not the slightest inconvenience is caused. 
(The same condition is found in the case of flea bites and mosquito 
bites.) The bite, so called, of the bedbug is produced by puncturing 
organs of the Hemipteron type already described. It is probable that 
the pierce of these stylets, unattended by contamination or specific 
poisons, would produce little pain. The local irritation and swelling 
is unquestionably produced by a specific poison of alkaline reaction 
secreted by the salivary glands and introduced in the act of feeding. 

The fact that the bedbug is obliged to feed at least five different 
times either upon the same or a different host, — the latter 'being the 
case most probably in rooming houses, hotels and crowded dwellings, 
— leads to the question of disease transmission. 

Disease Transmission. — In consequence of statements made by 
a number of authors that the bedbug is capable of transmitting plague 
and other septicemic infections, Nuttall l carried on a series of ex- 
periments with these insects. Mice were used in these experiments 
because they are very susceptible to the affections in question. He 
allowed the bugs to bite mice which had just died or were dying of 
anthrax, plague and mouse-septicsemia and then transferred them 
to healthy mice. Nuttall's experiments with anthrax are particularly 
instructive. Mice inoculated with anthrax died in from eighteen to 
twenty-four hours, after which they were placed in glass-covered dishes 
and hungry bugs introduced. As soon as the bugs had sucked a little 
blood they were removed to test tubes by means of a small camel's- 
hair brush and transferred to a shaved spot on healthy mice, by in- 
verting the tubes. Eight mice bitten by 124 infected bugs all remained 
healthy. Variations of this experiment gave similar results. It was 
found that the anthrax bacilli die in the stomach of the insect in 
forty-eight to ninety-six hours at 13° to 17° C. and in twenty-four 
to forty-eight hours at 37° C, and that the feces from the bugs con- 
tained living bacilli during the first twenty-four hours after feeding. 
In view of these experiments it may be concluded that infection 
through the bite of a bedbug either does not occur or is exceptional. 
That infection might occur if recently infected bugs were crushed while 
feeding and the punctured parts scratched is to be expected. 

Kala Azar. — Kala azar or dumdum fever is a highly fatal protozoal 
disease of India, having in many respects some similarity to malignant 
ague, but does not respond to quinine. The causative organism, 

1 Nuttall, 1899 (loc. cit.). 



BEDBUGS AND CONE-NOSES 73 

Leishmania donovani (Ross), is found in closely packed masses in the 
cells of the spleen and other viscera. These organisms, also known as 
Leishman- Donovan bodies, are said to be a non-flagellate stage which 
develops a flagellate stage in some other host. They are " ap- 
proximately circular or oval, 2.5 to 3.5 micra in diameter, clearly out- 
lined, and appear to possess a distinct cuticle, as they retain their shape 
and are rarely seen distorted in films. The two chromatin masses 
are characteristic, the large one staining slightly and the small one in- 
tensely with Romanowsky. The masses are usually situate opposite 
each other in the short axis of the parasite." 

Observations made by Patton x show that flagellate forms develop 
in from five to eight days in bedbugs after feeding on kala azar patients. 
Much circumstantial evidence strongly implicates both the Indian bed- 
bug Cimex hemipterus (C. rotundatus Patton) and the common Cimex 
lectularius as probable important transmitters of this disease. 

Relapsing Fever (Spirochetosis) . — The relapsing fevers traceable 
to Spirochceta duttoni (African form) and Spirochceta recurrentis 
(European form) are probably disseminated to some extent by the 
bedbug (Cimex lectularius) , since it has been shown by Nuttall 2 that 
the spirochetes survive in the bodies of bugs for a period of six days at 
a temperature of 12° C, and a much shorter period (six hours) at 20- 
24° C. He, however, succeeded in transmitting the disease to a mouse, 
in only one instance, by transferring thirty-five bugs from an infected 
mouse to an uninfected mouse. The evidence at hand seems to indicate 
that the bedbug is relatively unimportant. 

Control. — The habits of these parasites indicate in a measure the 
methods useful in their eradication in a given situation. The ease 
with which they secrete themselves in very narrow crevices provides 
safety against anything but very penetrating materials. Thus 
pyrethrum powder is only useful where the insects are quite exposed 
or within reach of a blower. The newer metal bedsteads are easily 
kept free from the bugs, while the old-fashioned wooden bedsteads are 
more difficult to handle; however, the writer has seen some very bad 
infestations entirely eliminated by the use of kerosene applied by means 
of a tail feather from a fowl. The more penetrating oils, such as gasoline 
and benzine which volatilize more readily, are to be recommended; 
however, greater precaution against ignition must be exercised. 

A thorough infestation of bedbugs will require a more strenuous 
campaign, extending even to the removal of all loose wall paper under 
which the bugs may have found a hiding place. Where the infestation 
has reached such proportions as to include several rooms or even 
an entire building, the more rapid and effective fumigation methods 
are far preferable, requiring less labor and producing better results. 

1 Patton, W. S., 1907. Scient. Mem. of the Gov. of India. Nos. 27 and 31 . 

2 Nuttall, G. F. H., 1913. The Herter Lectures. I. Spirochetosis. Para- 
sitology, Vol. 5, No. 4, pp. 262-274. 



74 MEDICAL AND VETERINARY ENTOMOLOGY 

Hydrocyanic acid gas is perhaps the most effective of fumigating 
agents, but the greatest care must be exercised in the process, 
since the gas is deadly to all forms of animal life and extremely 
penetrating. Rooms above apartments in which this gas is being 
applied should not be occupied during or immediately after the process. 
Sparrows have been known to drop from the eaves of houses in which 
cyanide fumigation was going on. However, with proper precautions 
very little danger is involved. 

To prepare a room for cyanide fumigation, all wet or moist food- 
stuffs must be removed (dry materials such as flour, meal, bread, etc. 
need not be removed) ; if the house is occupied, there must be no crevices 
leading from the room to be fumigated to occupied rooms. It is best that 
the house should be vacated during the process, — this need be for only 
a period of five or six hours. Fumigation should not be undertaken 
when it is cold ; a temperature of about 70° F. gives best results. If 
there is a fireplace in the room, this should be covered with a blanket 
or other covering. All crevices, such as occur around the doors and 
window sashes, keyholes, etc., must be tightly covered with strips of 
paper pasted in place with a very dilute flour paste, or as some have 
found, merely soaked in water. The cubic contents of the room must 
be estimated and sufficient ingredients provided to do the work. One 
ounce of potassium cyanide for every one hundred cubic feet of space is 
necessary. To generate the gas sulphuric acid and water must be 
used. The following proportions are needed for one hundred cubic 
feet of space : — 

Potassium cyanide (98 %) 1 oz. 

Sulphuric acid (about 66° Beaume) . . . . . 1 fluid oz. 
Water • 3 fluid oz. 

or for 130 cubic feet of space : — 

Sodium cyanide (129 %) 1 oz. 

Sulphuric acid 1 fluid oz. 

Water 2 fluid oz. 

To proceed place the water (in proper proportion) in a heavy two 
to three gallon earthen jar placed on thick folds of paper to catch 
spattered liquid, then slowly add the sulphuric acid (water always first, 
then the acid), lastly drop a paper bag containing the cyanide into the 
liquid, holding same at arm's length, and immediately beat a hasty re- 
treat, carefully closing the door. After the expiration of about iive 
hours, open the windows from the outside and permit the room to 
"air" until the "peach kernel" odor has disappeared. The contents 
of the jar should be carefully disposed of. 

In treating an entire building the operator must always begin at 
the top and work downward. 

To fumigate with sulphur, a very efficient method to destroy bed- 
bugs and other vermin, flowers of sulphur or lump sulphur is used. The 






BEDBUGS AND CONE-NOSES 75 

rooms are prepared as for hydrocyanic acid gas fumigation. All metal 
objects and fine, delicately tinted fabrics must be removed, if possible ; 
metallic objects may also be covered carefully or, what is better, coated 
with vaseline. Sulphur, at the rate of four pounds to every 1000 cubic 
feet of space, is placed in a shallow iron pot or skillet which is placed on 
bricks or stones in a tub in which there is a little water in order to pre- 
vent spilling out and igniting the floor. The sulphur is easily ignited 
by pouring over it a few ounces of wood alcohol (or grain alcohol) and 
then lighting it with a match. Fumigation must continue for at least 
two hours, when the doors and windows should be opened to ventilate 
the room before occupancy. 

While sulphur fumes (sulphur dioxid) are extremely useful against 
insects and other animal life, such as rats and mice, the liability to bleach 
fabrics and paper, and tarnish metals is against this method unless 
conditions are absolutely dry. 

The natural enemies of the bedbug, such as red ants and cockroaches, 
do not enter in as practical factors, inasmuch as they are just as un- 
desirable as the bedbug itself. 

Repellents have had little or no consideration ; however, old 
residents, who have had to live under conditions where bedbugs were 
plentiful, e.g. taverns and inns, state that they have found great relief 
in the use of leaves of the " bay tree " merely placed among the 
bedding. 

B. The Cone-Noses 
Order Hemiptera, Family Reduviidce 

The Reduviidae. — Members of the family Reduviidae as typical 
representatives of the order Hemiptera, suborder Heteroptera, have the 
basal half of the wing covers thick and leathery. The mouth parts, 
(Fig. 26), which are piercing structures par excellence, consist of a three- 
jointed proboscis extending from the extreme distal end of the head, 
and directed backward between the fore coxae while at rest. The rather 
cone-shaped form of the head gives rise to the popular term " cone-noses " 
applied to certain of these insects. The long, slender, four-segmented, 
naked antenna? (basis for the term Gymnocerata) are located in front 
of the prominent eyes on the border of the head. The Reduviidae are 
predaceous in their feeding habits to a marked degree, hence the term 
"assassin bugs." Creeping slowly toward their victims, these assassins 
suddenly pounce upon the unsuspecting insect, into which are thrust the 
strong, sharp, needle-like stylets and the juices sucked out. The victim 
is ordinarily another insect ; however, there are several species of cone- 
noses which evidently feed on mammalian blood if the opportunity is 
offered. 

Many of the recorded cases of cone-nose bites indicate that the 
"bite" inflicted was not "premeditated," but quite accidental or 



76 MEDICAL AND VETERINARY ENTOMOLOGY 

rather an act of self-defense. The writer's first experience with a 
cone-nose was while incautiously plucking a leaf from a tree. The 
bite was instant and the pain most intense, and though the wound was 
on the finger the pain seemed to extend to the head and was followed by 
a feeling of faintness. The recovery, however, was but a matter of 
less than half an hour with no after effects except for a slight local 
cellulitis. 

The kissing bug scare of 1899 was traced to the presence of what 
was perhaps an unusual abundance of Reduviidse of a given species, 
and the fact that individuals were commonly bitten about the lips and 
face gave rise to the above popular cognomen. Many of these bites were 
pretty surely induced by grasping the insects with the fingers as they 
flew into the face at night. The common kissing bug (Opsicoetes 
(Reduvms) personatus) is strongly positively phototropic, hence dashes 
vigorously at a light and often into the face of any one near by. 

Opsicoetes (Reduvius) personatus Linn, is one of the commoner species 
of Reduviids, having a wide distribution, ranging over the entire eastern 
part of the United States as far west as the Rocky Mountains. It is 
originally a European form and has now become well-nigh cosmopolitan. 
This insect is about two centimeters in length, and is coal black. The 
prothorax in dorsal aspect has two prominent tubercles or swellings, 
due to a median, dorsal, longitudinal groove and a transverse posterior 
groove. The young present a very curious masked appearance because 
of a covering of lint and dust, which adheres to the body by means of 
a sticky secretion. 

This species is commonly known as the " kissing bug " which pro- 
vided much " story " material for the newspapers of the Eastern states 
during the summer of 1899. It inflicts a very painful wound. Howard l 
quoting LeConte writes : " This species is remarkable for the intense 
pain caused by its bite. I do not know whether it ever willingly 
plunges its rostrum into any person, but when caught or unskillfully 
handled it always stings (pierces). In this case the pain is almost 
equal to that of the bite of a snake, and the swelling and irritation which 
result from it will sometimes last for a week. In very weak and irri- 
table constitutions it may even prove fatal." 

Conorhinus sanguisuga Lee. is known as the " blood-sucking cone- 
nose," also called the " big bedbug." Conorhinus is probably a typical 
South American and Mexican genus, but this species is commonly found 
in the Southern states of the U. S., occurring as far north as southern 
Illinois and Ohio. The " big bedbug " has secured this name for 
itself because of its frequent presence in bedrooms and beds. Since 
several species of the Reduviids are known to capture and feed on bed- 
bugs it is quite likely that this species shares this habit, probably pre- 

1 Howard, L. O., 1899. The Insects to which the name "Kissing Bugs" 
became applied during the summer of 1899. U. S. Dept. of Agric, Div. Ento. 
Bull. No. 22. 



BEDBUGS AND CONE-NOSES 



77 



ferring human blood second-hand, but will just as soon partake of this 
luxury at first hand if the opportunity offers itself. 

This cone-nose is from 2 to 2\ cm. in length, and is dark brown in 
color with pinkish segmental markings on the dorsal borders of the ab- 
domen and on the tips and bases of the hemi-elytra. In other respects 
it is a typical Reduviid of the fiercest appearance. The bite, if anything, 
is even more severe than that of the former species and results in more 
uniform symptoms. Because of the uniform character of the symptoms 
Marlatt suggests that a specific poison is injected into the wound. 
There is ordinarily " a burning pain, intense itching and much swelling " 
with the appearance of " red blotches and welts all over the body and 
limbs." The effects of the bite may last for months; however, they 
usually disappear within a few days. 

Conorhinus protractus Uhler (Fig. 67), commonly known as the 
" China bedbug," is a widely distributed Pacific Coast species and is 
responsible for the large majority 
of cone-nose bites in California, 
where it has been reported from 
many localities. This species is 
frequently found indoors and 
averages 18 mm. in length, and is 
nearly dead black in color through- 
out. The abdomen is broad with 
a wide margin exposed around the 
narrow folded wings lying in the 
dorsal concavity. Van Duzee re- 
ports collecting this species com- 
monly in the nests of wood rats. 

The symptoms produced by 
Conorhinus protractus are ordi- 
narily described by local physi- 
cians, viz. : "In a few minutes 
after a bite the patient develops 
nausea, flushed face, palpitation 
of the heart, rapid breathing, rapid pulse, followed by profuse urticaria 
all over the body. The symptoms vary with individuals in their 
intensity." Inquiries with regard to this species are most frequent 
during May and early June. 

Melanolestes picipes H. S. resembles the above very closely, but is 
more slender and is a typical field species, as is M. abdominalis H. S. 
and Apiomerus crassipes Fabr., the latter a heavy-set, pilose, droll-looking 
creature, — all of these inflict painful bites. 

Rasahas biguttatus Say, the " two-spotted corsair," is quite common in 
the Southern states, Cuba and South America, and, according to Van 
Duzee, giving way in the northwest and California to R. thoracicus 
Stal (Fig. 68), a very closely related form. The writer has taken this 




Fig. 67. — A cone-nose, Conorhinus protrac- 
tus, also known as the China bedbug. X 2.1. 



78 



MEDICAL AND VETERINARY ENTOMOLOGY 




latter species in many parts of California from the Imperial Valley to 
the Sacramento, but has only a few records of its attacking human 

beings, though Howard 1 reports 
thus : " Dr. A. Davidson, formerly 
of Los Angeles, in an important 
paper entitled ' So-called Spider Bites 
and their Treatment ' published in 
the Therapeutic Gazette of February 
15, 1897, arrives at the conclusion 
that almost all of the so-called spider 
bites met with in southern Cali- 
fornia are produced by no spider at 
all but by Rasahus biguttatus. The 
symptoms which he describes are as 
follows : Next day the injured part 
shows a local cellulitis with a dark 
central spot ; around this spot there 
frequently appears a bulbous vesicle 
about the size of a ten-cent piece and 
filled with a dark grumous fluid ; a 
smaller ulcer forms underneath the 
vesicle, the necrotic area being generally limited to the central part, 
while the surrounding tissues are more or less swollen and somewhat 
painful. In a few days with rest and proper care the swelling sub- 
sides, and in a week all traces of 
the cellulitis are usually gone. On 
some of the cases no vesicle forms at 
the point of injury, the formation 
probably depending on the constitu- 
tional vitality of the individual or 
the amount of poison introduced." 
This species has also the repu- 
tation of being a bedbug hunter. 

Life History. — Though the life 
history (Fig. 69) of but a very few 
species of Reduviid has been worked 
out completely, it seems likely that 
all the species mentioned have but 
one generation a year. The eggs of 
Conorhinus sanguisuga are said to be 



Fig. 68. — The "two-spotted corsair, 
Rasahus biguttatus var. thoracicus. X 2.1 




Fig. 69. — Egg (left) and larva (right) of a 
cone-nose, Conorhinus protractus. X 4.4. 



white at first, then yellow, and finally become pinkish in color ; they are 
barrel-shaped and are deposited on end, the compact mass of twenty- 
five to thirty forming a rather regular five or six sided figure. The young 
insects emerge in about twenty days. The metamorphosis is simple. 
Conorhinus protractus deposits its large white eggs (few in number) 
1 Howard, L. O., 1899 (loc. cit). 



BEDBUGS AND CONE-NOSES 79 

during midsummer and these hatch ordinarily in about three weeks, 
the first molt taking place in seven or eight days after hatching. 

Chagas Disease (Brazilian Trypanosomiasis). — In 1909 Chagas 1 
reported from Brazil an endemic human trypanosomiasis. This disease 
occurs in its acute form in infants and in its chronic form in adults. 
It is characterized by an irregular fever, anaemia, enlargement of 
lymphatic glands, particularly an enlargement of the thyroid. The 
causative organism Schizotrypanum cruzi Chagas is said to be present 
in the peripheral blood of children during the fever, but in adults and 
children during later periods occurs in the cells of the thyroid, bone 
marrow and other tissues, resembling Leishmania during its segmenta- 
tion stage. The flagellate form is said to enter the lungs of the host, 
where the flagellum is lost and an oval form is taken on. 

Chagas found theprotozoonin the intestine of a cone-nose, Conorhinus 
megistus Burm. (also referred to the genus Tri atom a), and succeeded in 
transmitting it through the cone-nose to rodents. As reported, the in- 
cubation period (after the bite) varies from ten to fourteen days. 

There is some difference of opinion as to mode of transmission; 
Chagas evidently believing that the parasites multiply in the intestine 
of the cone-nose, passing thence to the salivary glands, infection taking 
place directly with the bite. Brumpt, 2 on the other hand, says that 
infection results through the infective dejecta of the insect deposited 
upon the skin of the host when the insect bites, inoculation taking 
place through the mucous membrane of the mouth, inasmuch as the 
cone-nose usually bites the face and lips of sleeping persons. 

Control. — The conspicuous size of these insects should make it an easy 
matter to find them in bedrooms, when it is known that they are common. 

Since they are attracted by light at night, it is wise to screen windows 
and doors. Considerable precaution should be exercised when a speci- 
men has alighted on the face or hands ; do not grasp it between the 
fingers, this will pretty surely cause the insect to thrust its proboscis 
at once into the flesh. A quick snap of the finger will generally re- 
move the intruder without any bad results, and the insect can then be 
crushed. They are, however, rapid in their movements. 

Treatment for the Bite. — Treatment for the bite of cone-noses 
has usually a twofold object; first, to neutralize the specific poison of 
the cone-nose, and secondly, to prevent extra infection which is liable 
to occur because of the indiscriminate feeding habits of the insect. 
Bathing the wound with corrosive sublimate in proportions of 1 to 1000 
is said to give good results, as will also ammonia. 

1 Chagas, C, 1909. Ueber eine neue Trypanosomiasis des Mensehen. 
Memorias do Instituto Oswaldo Cruz, I, pp. 159-218. 

2 Brumpt, E., 1913. Immunite parti elle dans les infections a Trypanosoma 
cruzi transmission de ee trypanosome par Cimex rotundatus. Role regulateur 
des notes intermediaires. Passage a travers la peau. Bull. Soc. Path. Exot., 
Vol. VI, No. 3, pp. 172-176. (Abstract in the Review of Applied Ento., Ser. D., 
Vol. I, No. 7.) 



CHAPTER IX 
MOSQUITOES 

Order Diptera, Family Culicidce 

General Characteristics. — As members of the Order Diptera, 
mosquitoes partake of the general characters of the order; namely, 
reduction of the metathoracic (posterior) pair of wings, in place of which 




Fig. 



70. — Crane fly (Tipula), often mistaken for a mosquito, 
immediately behind the wings. X 1. 



Halteres visible 



there occurs a pair of tiny knobbed organs known as the halteres or 
balancers, most distinctly visible in the crane flies (Tipulidse) (Fig. 70). 
The Diptera are commonly divided into two suborders, — first, 
Nematocera, in which the antennae are many-jointed and filamentous, 

80 



MOSQUITOES 



81 



as in the mosquitoes (Culicidse), crane flies (Tipulidse), midges 
(Chironomidse) and buffalo gnats (Simuliida?) ; secondly, the Brachy- 
cera, in which the antennae are short and not thread-like, as in the 
horseflies (Tabanidse), house flies (Muscidse) and botflies (CEstridse). 

The Culicidse (mosquitoes) are distinguished from all other Nema- 
toceran Diptera by (1) the character of the wing venation (Fig. 71), 
which varies also specifically within the family ; (2) by the presence of 
characteristic scales fringing the wings and more or less abundant on 
the body and head (Fig. 78). The family may be divided into two 





axillaeu ve\n 



SV vtin 



Fig. 71. — Showing (upper figure) scaly wing of a mosquito with spots of Anopheles; 
(lower figure) wing venation of a mosquito with veins and cells named and numbered 
for systematic purposes. X 23. 

divisions : the Corethrinse or short-beaked, non-blood-sucking mosquitoes, 
represented by the genus Corethra (Fig. 72), and the Culicinse or 
long-beaked, blood-sucking true mosquitoes. The males of all mos- 
quitoes are non-blood-sucking. 

Nearest Allies. — There are many Dipterous insects which may be 
easily mistaken for mosquitoes unless a careful microscopical examina- 
tion is made. For all practical purposes the characteristics referred 
to above should serve to determine whether the insect in hand is a 
mosquito or not. It is true that other families of Diptera are in some 
cases provided with scales, but other simple characters to be pointed 
out here should serve to eliminate these. The most commonly mistaken 
insects are members of the family Chironomidse, the midges (Fig. 73). 
According to Williston these may be distinguished from mosquitoes in 
that the costal vein is not continuous on the posterior side of the wing. 



82 



MEDICAL AND VETERINARY ENTOMOLOGY 



The wings are usually bare or in some may be hairy. The proboscis 
is short, and in all except the " punkies " or " no-see-ums " are non- 
blood-sucking. These latter are tiny gnats, but vicious biters. The 
most common Chironomids which often occur in enormous swarms over 
or near swamps have bare wings, plumose antenna? and do not bite. 

In size and general 
form they resemble 
mosquitoes very 
closely, particularly 
male mosquitoes. 

Members of the 
family Tipulida?, crane 
flies or " daddy long- 
legs " are commonly 
mistaken for mosqui- 
toes. The commoner 
species are usually dis- 
tinguished by the pres- 
ence of a V-shaped 
suture situated dorsally 
on the thorax (mesono- 
tum) (Fig. 74) and by 
the blunt, non-piercing 
mouth parts. The 
wings are usually 
devoid of scales or 
hairs (some exceptions) . 
Other mosquito-like 
Diptera are the Dixa 
midges (Fam. Dixidse), 
in which the mouth 
parts are blunt and the 
wing veins are devoid 
of scales; the family 
Psychodidse includes 
the moth-like flies 
which are densely cov- 
ered with hairs and are 
not easily mistaken for 
mosquitoes The " papatici flies," members of this family and of the 
genus Phelebotomus, are blood-sucking and occur in the Philippine 
Islands, parts of Asia, Africa and South America. 

Life History. — A general statement of life history as applied to 
mosquitoes is not possible if the time required for complete transforma- 
tion is desired, inasmuch as this varies considerably for the genera and 
even for species. However, it may be said with certainty that all mos- 




Fig. 72. — Corethra, easily mistaken for a mosquito, is an 
insect belonging to the family Culicidse (note scaly 
wings) but is non-blood-sucking. (After Smith.) 
X 12. 



MOSQUITOES 



83 



quitoes pass through a complex metamorphosis represented by the usual 
stages, egg, larva, pupa and imago (Fig. 75). The larvae are commonly 
called " wrigglers " and the pupae " tumblers." Water in which to 
pass the larval and pupal stages is absolutely essential. The eggs may 
be deposited on wet mud and the larvae may exist for some hours in 
similar situations. With reference to this Howard states that " In 
no case, however, were we able to revive larvae in mud from which the 
water had been drawn off for more than forty-eight hours, and after 
twenty-four hours only a 
small proportion of the 
larvae revived." 

The eggs of mosqui- 
toes are deposited from 
early spring to early 
autumn, and in warmer 
parts active " wrigglers " 
may be found through- 
out the year. The writer 
has found nearly full- 
grown larvae in parts of 
California in January and 
pupae from which occa- 
sional imagines emerged 
during the month of 
February. These over- 
wintering larvae are quite 
certainly from eggs de- 
posited late in the autumn 
and in which growth is 
very slow. Mosquitoes 
which make their appear- 
ance early in the spring 
are, as a rule, individuals 
which have been in hiber- 
nation during the winter. 

Probably about ten 
days is the shortest time 

for any of the commoner species of mosquitoes to pass through the 
various developmental stages ; Howard gives the time for Culex pungens 
as " sixteen to twenty-four hours for the egg, seven days for the larvae, 
and two days for the pupa." From this rather short life-history period 
the time required to pass through the same transformation may be two 
or three weeks, and under lower temperature conditions, several months. 
At a maintained temperature of 24° ± 1° C. Culiseta incidens required 
about twenty -four hours for the eggs to hatch, the larvae molted on the 
fourth day after hatching and again on the eighth day, pupating on the 




Fig. 



"3. — A midge (Chironomidae), often mistaken 
for a mosquito. (After Osborn.) X 12. 



84 



MEDICAL AND VETERINARY ENTOMOLOGY 



eleventh day, thus giving about ten days for the larval period; mos- 
quitoes emerged on the second day after pupation, requiring about 
thirty-six hours for this stage. The mosquitoes were given a suck of 
blood within twenty-four hours and in four days thereafter deposited 
eggs. This gives a period of about eighteen days from egg to egg under 
favorable conditions. 




Fig. 74. 



Head and thorax of a crane fly (Tipulidse) , showing 

(h) and characteristic v-shaped suture on thorax (v). 



, halteres 



The longevity of the female mosquito is a matter not so easily deter- 
mined because of the conditions needed in ascertaining this ; outdoor 
observations naturally offer a great handicap to the observer. By 
feeding mosquitoes on ripe banana and blood, it has been possible to 
keep them in captivity as long as two months, but this is probably 
longer than the average, because by far the greater number of females 
die in captivity within two or three weeks, while the males only live 
three or four days. It should be remembered, of course, that mosquitoes 
in hibernation may live as long as six or seven months. It is quite 
probable that the average active lifetime of the female mosquito under 
natural conditions will be found to be pretty close to thirty days, as the 
writer has observed for several species of Sarcophagid and Muscid flies. 

Internal Anatomy. — To be prepared to study the relation of mos- 
quitoes to such diseases as malaria and filariasis the student must be 
familiar with their internal anatomy, which offers specializations of 
importance. 



MOSQUITOES 



85 



The alimentary canal is separable into three regions, the fore-, 
mid- and hind-gut, each of which is again subdivided into more or less 
distinct divisions (Fig. 76). Thus the fore-gut consists of the sucking 



' 




Fig. 75. — Illustrating the life history of a mosquito (Anopheles quadrimaculatus) . a. egg: 
b. larva or wriggler (viewed from above) ; c. pupa or tumbler ; d. adult. X 5. 



tube of the proboscis, the pharynx, including pumping organ and the 
esophagus with its diverticular (two or three in number and known as 
food reservoirs) ; the mid-gut consists of a narrower anterior portion 




Fig. 76. — Internal anatomy (in part) of a mosquito, a. head; b. thorax; c. abdomen; 
ant., antenna; pip., palpus ; prb., proboscis ; br., brain; sbbt., subesophageal ganglion; 
nch., ventral nerve chord ; ph., pharynx ; oes., esophagus ; res., food reservoir, of which 
there are three (esophageal diverticula) ; prov., pro ventri cuius (false) ; st., stomach or 
mid-gut ; il., ileum ; col., colon ; red., rectum ; mpgt., Malpighian tubules ; sal., salivary 
gland ; salvsvr., salivary reservoir ; said., salivary duct. (Adapted after various 
authors and based on dissections.) 

(false proventriculus) and a wider posterior portion (stomach) occupying 
the thorax and much of the abdomen, and limited posteriorly by the 
origin of the five Malpighian tubules which indicate the beginning of the 
viscera or hind-gut ; the hind-gut is bent on itself several times and 
consists of the narrow, longer ileum, the colon and what is arbitrarily 
termed rectum marked anteriorly by a slight constriction. 



86 



MEDICAL AND VETERINARY ENTOMOLOGY 



The salivary system consists of two sets of salivary glands (right and 
left), three glands to each set (Fig. 76). These organs are situated 
ventrally in the thorax near the neck. Each set of glands empties into 
a duct which combines with the opposite one to form the common 
salivary duct. This common duct empties its contents into the 
esophagus through the salivary receptacle close to the base of the 
proboscis. 

The reproductive system of the female mosquito occupies the posterior 
portion of the abdomen and comprises a pair of ovaries joined by a pair 
of oviducts terminating in the vagina and ovipositors, one to three 
(depending on the species) ; spermathecw are present. The spermathecse 
of an impregnated female contain myriads of spermatozoa, and the 
ovaries when mature occupy the larger part of the abdomen. 




Fig. 77. — Heads of mosquitoes, showing relative length of palpi, 
ing the two main subdivisions of mosquitoes, a. Culicine ; b. 
c. Anopheline. 



Useful in distinguish- 
male of either group ; 



Sexual Differences. — The males of many species of mosquitoes are 
provided with plumose antennae (Fig. 77) ; in the female, as a rule, 
these organs are slender, thread-like and covered with short lateral 
hairs. In the males the palpi are with few exceptions long (as long or 
longer than the beak), conspicuous, jointed organs and quite hairy (Fig. 
776). In the iEdinse the palpi are short in both sexes. Inasmuch as 
males do not feed on blood they are less frequently found about human 
habitations. Sweeping with the insect net in grass or other low vege- 
tation will usually result in the capture of males if there is a breeding 
place near and it is the proper season. 

Characters of Systematic Value. — Although most authors have 
discarded the relative length of palpi as a useful character in separating 
the Culicinse into three divisions or tribes, we still find this very useful, 
particularly in localities where malaria control work is in progress. On 
this basis the tribe Culicini includes mosquitoes in which the palpi of 
the females are less than half as long as the proboscis (Fig. 77a) ; the 
tribe Anophelini includes mosquitoes in which the palpi of the females 



MOSQUITOES 



87 



are nearly or quite as long as the 
both tribes are provided with palpi 
cis, except in what were formerly 
palpi of both males and females 
are short; the palpi are com- 
monly quite hairy, as are the 
antennse (Fig. 77b). 

The determination of the 
genera and species by some 
authors is based quite largely 
on the character of the scales. 
The scales on the head and 
body are of several varieties, as 
shown in Fig. 78. The occur- 
rence and arrangement of these 
scales on the head, thorax, ab- 
domen and wings provides a 
basis for distinguishing the 
genera, as illustrated by Fig. 
79. Stephens and Christophers 
state, " All mosquitoes belong- 
ing to the genus Culex have on the head 



proboscis (Fig. 77c). The males of 
as long as or longer than the probos- 
designated the JEdini, in which the 




Fig. 78. — Varieties of Culicid scales, a, b, c, 
head scales, (a) narrow curved, (6) upright 
forked, (c) fiat; d-h, thoracic scales. (Re- 
drawn after Stephens and Christophers.) 



(1) narrow curved and 



(2) upright forked, but only (3) a few flat scales laterally ; whereas all 




Fig. 79. — Occurrence and arrangement of scales on the heads of mosquitoes, (a) 
Stegomyia ; (b) Anopheles ; (c) Culex. (Redrawn in part after Stephens and Chris- 
tophers.) 



mosquitoes belonging to the genus Stegomyia have on the head (1) no 
narrow curved scales, (2) a few upright forked and (3) flat scales, cover- 
ing the whole of the head." In Anopheles there are " upright forked 
scales only on the head." 



88 



MEDICAL AND VETERINARY ENTOMOLOGY 



The ungues or tarsal claws are also useful characters in local classifi- 
cation. In some species the claws are not toothed and in others the 
claws are toothed. 

The spotting of the wings is not a safe character to separate the 
Culicini from the Anophelini, although all except two or three species of 
Culicines have unspotted wings, and all but one or two Anopheline 
species have spotted wings. Culiseta (Theobaldia) incidens, a very 
common Culicine mosquito of California and elsewhere, has con- 
spicuously spotted wings. 



Anopheline Mosquitoes 

Adults. — As already stated, the Anophelini are roughly distinguished 
from the Culicini by the presence of long palpi in both males and females 

(Fig. 77). The proboscis is always 
straight and the scutellum is simple, 
never trilobed (Stephens and Christo- 
phers). The commoner Anopheline 
species of North America have also a 
characteristic resting attitude (Fig. 80), 
i.e. the body is usually thrown up at 
an angle with the surface upon which 
the insect is resting ; this angle is the 
greatest when the individual is resting 
on the ceiling, for the reason that 
gravity acts then more strongly on the 
heavy abdomen. When resting on a 
table or other horizontal surface, this 
angle is not so noticeable, but in all cases 
the proboscis is nearly or quite on a line 
with the body, whereas in the Culicini the 
beak and body form a distinct angle. 

The hum of Anopheles is all but in- 
audible; where the Culicine mosquito 
produces a high-pitched, tantalizing tone 
and is quickly brushed away, the Anoph- 
eles may alight and actually proceed to 
pierce the skin of the victim before it is 
detected. 

Eggs. — The Anopheline female de- 
posits from 75 to 150 ova, while the 
Culicini deposit a larger number, often 
from 250 to 450. In the former case 
(including Mdes (Stegomyia) calopus and 
other iEdini) the individual eggs lie flat 
on the surface of the water and often form 




Fig. 80. — Characteristic atti- 
tude of adult mosquitoes at 
rest. a. Anopheles with body- 
normally at an angle of from 
25° to 55° with the surface ; b. 
Culex, with body parallel. X 8. 



MOSQUITOES 



89 



geometrical figures with each other, owing to their peculiar form; in 
the latter (Culicini) (excepting M&es (Stegomyia) calopus and other 
iEdini) the eggs are placed on end, forming a boat-shaped pack or raft 
(Fig. 81). 

On examination it will be seen that the individual canoe-shaped 
Anopheline egg is provided on the upper surface with a pair of floats 





Fig. 81. — Mosquito eggs, (a) egg rafts of Culicine ; 
(6) egg masses of Anopheline. (After Howard.) 

midway on either side and with cor- 
rugated edges extending nearly the 
length of the egg (Fig. 82a). The in- 
dividual Culex egg tapers decidedly at 
the upper end and terminates at the 
base in a globular organ called the " micropilar apparatus " (Fig. 826). 
Larvae. — The larva? of Culicine mosquitoes (Fig. 83a) are always 
suspended from the surface of the water at a decided angle with only 
one portion, the anal siphon, 
touching and penetrating the film, 
while in Anophelinse (Fig. 836) 
the larvse lie horizontal with at 
least several body segments com- 
ing dorsally in contact with the 
film. At the point of contact each 
segment is provided with a group 
of hairs arranged fanlike. The 
eighth abdominal segment in both 
groups is provided with a special- 
ized organ through which the 
tracheae (breathing organs) come 
in contact with the outer air. In 
the Culicini this apparatus is pro- 
longed into a definite breathing 
tube (siphon), while in the Anophelini this tube is absent, or only 
slightly protuberant and not chitinous as in the former (Fig. 83). 
So abundant are the wrigglers at times that a small pool may be 
literally black with them. Dr. J. B. Smith made some observations 
with reference to numbers in Anopheles crucians and found that a 





Fig. 82. — Individual mosquito eggs. (a) 
Anopheles ; (6) Culex ; (c) Stegomyia. 
(Adapted after Mitchell.) 



90 



MEDICAL AND VETERINARY ENTOMOLOGY 



pond with an area of 1894 square feet contained 10,636,700 wrigglers, 
roughly ten and one half millions, or 5616 to every foot of area. 

The movements of Anopheline larvae are very much more jerky 
than those of the Culicine, in which the wriggling motion is worm-like. 
The former are also not so easily seen as are the latter, probably owing 
to their horizontal position at the surface of the water. On wading 
into a swamp no larvae may be visible, but on looking backward into 
the now muddy water, the larvae may be plainly seen, distinctly out- 
lined against the murky background. 

A close examination of the feeding Anopheline larvae will show that 
the head is turned dorsally and that the smaller organisms (animal and 




Fig. 83. — Mosquito larvae in natural position 
in the water, (a) Culicine ; (b) Anopheline. 



vegetable) near the surface form the 
main objects of diet. The Culicine 
larvae usually feed on organisms 
located at the bottom of shallow pools and at the sides of vessels, etc. 

Pupae. — The pupae or nymphs of all mosquitoes are very similar. 
In all cases, instead of the single posterior breathing apparatus of the 
larva, there are present a pair of breathing trumpets (right and left) 
located on the thorax, i.e. anteriorly. The position of these trumpets 
in the two general groups of mosquitoes is different and fairly distinctive, 
i.e. they are located farther forward on the thorax in Anophelini, near 
the middle, and open broadly in this group, being more slender and 
relatively longer in the Culicini. 

In position the two groups also differ somewhat, i.e. the Anopheline 
pupae hang more horizontally, and the heavier " head-end" is relatively 
longer. 

Life History. — As in all other mosquitoes and insects in general the 
life history depends greatly on temperature. In early spring and late 
autumn the development is retarded, owing to the lower average tempera- 
ture. 

In midsummer the egg stage is rarely longer than twenty-four 
hours and often nearer twelve hours duration. The larva emerges by 
splitting the egg (Fig. 84) (or in the Culicini by pushing the bottom 



MOSQUITOES 



91 



from the egg) and begins its existence in the water, usually clinging 
close to debris or scum. The larval stage is most easily affected by 
temperature, but lasts usually from twelve to fifteen days, during which 
time the skin is shed several times. The change into the nymphal or 
pupal stage is undergone very rapidly and usually occurs overnight; 




Fig. 84. — Anopheles mosquito larva just emerged from the egj 



X 50. 



great numbers may undergo this change in the early part of the night 
between nine o'clock and midnight. This stage is comparatively short, 
requiring seldom over thirty-six hours. At the end of this time the 
pupal skin bursts along the mid-dorsal side, the pupa in the meantime 
having straightened out. In a few minutes the adult has pulled itself 
out of the pupal skin, and quietly balancing itself, remains on top of its 
cast skin until its wings are sufficiently dry to permit it to fly away. Thus 
it must be inferred that the process of emerging requires a very quiet 
body of water, otherwise the mosquito would be submerged and perish. 
Duration of Adult Life. — As a rule the newly emerged females will 
suck blood after a period of about twenty-four hours. Numerous ex- 
periments tried on the male mosquito as well as extensive field observa- 
tions seem to give conclusive evidence that this sex does not possess 
the blood-sucking habit, living exclusively on the juices of plants and 
" plain " water. However well one may care for the males they in- 



92 MEDICAL AND VETERINARY ENTOMOLOGY 

variably die within a week, usually in about three days, and it is quite 
probable that very little nourishment is taken during this time. 

In captivity the mosquito mortality is very high, and it is therefore 
not a satisfactory plan to estimate the average length of life on the 
basis of laboratory observations. Basing an estima-te on the relative 
abundance of Anopheline mosquitoes in a given district during several 
weeks after careful control measures are inaugurated, it seems safe 
to say that the average life of the adult female mosquito is between thirty 
and forty days, perhaps nearer thirty. This does not, of course, refer 
to hibernation. Ordinarily the female mosquito dies shortly after she 
has deposited her eggs. 

Flight. — It is a matter of common observation that Anopheline 
mosquitoes are not strong fliers. If Anopheles are found, one can 
rest assured that their breeding place is somewhere very near, usually 
within two hundred yards. They are seldom found over a mile away. 
However, if the breeding place of these insects is connected with human 
habitations by means of low herbage at close intervals, this will afford 
a ready means of advance. On the other hand, it seems that a belt of 
trees tends to act as a barrier. 

Unlike certain other species of mosquitoes, notably salt-marsh mos- 
quitoes, the Anopheles are not readily carried by the wind, inasmuch as 
they take to cover even in a moderate breeze and cling to vegetation. 

Hibernation. — The writer has been bitten by Anopheles mosquitoes 
in California as early as February 12, and at noonday at that, and a 
specimen was captured in the act of flying about in a church on the first 
of January. Since all breeding had ceased in late October, it must be 
assumed that these were hibernated individuals which had been induced 
to leave their shelters by the appearance of balmy days. In the colder 
Eastern states there are no winter days when it is balmy enough to 
induce mosquitoes to come forth from their places of hibernation. 

The first case mentioned was a normal response to the usual early 
spring days in California, where breeding begins correspondingly early. 
The day before, i.e. February 11, mosquitoes were seen emerging from be- 
neath a schoolhouse which had afforded a place of hibernation during the 
heavy rains. This place had probably been sought early in November. 

The above and other similar experiences afford ample evidence that 
Anopheles mosquitoes which have been in hibernation are active on 
emerging even by daylight (noonday) and bite fiercely during that time. 

Yellow Fever Mosquitoes 

Adults. — Mosquitoes belonging to what was formerly known as 
the genus Stegomyia (now ^Edes), of which there were twenty or more 
species, are all beautifully marked with silvery white or yellowish white 
bands and stripes on a nearly black background, whence the name 
" tiger mosquitoes " applied to the members of this group. 



MOSQUITOES 




94 



MEDICAL AXD VETERINARY ENTOMOLOGY 



-.-^hoTAC'lC 

halrtujts 



^abdonuna.1 
hair tuj-ts 



anal sipho.n 



combs or pectens 
5* anal seg 



"tracheal ©ills 



JEdes calopus Meig. (Stegomyia fasciata Fabr.), with which we are 
principally concerned, has a " lyre-like " pattern (Fig. Sod) on its back 
(thorax), i.e. two outer curved yellowish white lines and two median 

parallel lines. The legs are also 

Cotaru mouth brushes • 1 1 j i ,i i" . l 

3 V. conspicuously banded, the distal 

portion of each segment being 
whitish and the terminal tarsal 
joint entirely white. An exami- 
nation of the head in this genus 
shows it to be covered with 
broad flat scales (Fig. 79) with 
only a single row of upright 
forked scales. 

The yellow fever mosquito is 
commonly known as the " day- 
flying mosquito." This, how- 
ever, only applies to the younger 
individuals up to six or seven 
days, after which they become 
nocturnal like other mosquitoes. 
The distribution of the yellow 
fever mosquito marks it as a 
tropical and subtropical species. 
Theobald refers it to 38 degrees 
north and south latitude. How- 
ard x points out that this mos- 
with parts used quito " does not thrive below a 
(Adapted after temp erature of 80° F., so that in 
a uniform climate with a tem- 
perature much below 80° the species will not continue to exist." 
The same author also states that it is probable that it has a wide range 
south of the Mason and Dixon line in the United States. Yet California, 
owing probably to its cold nights, is free from this species, at least 
north of San Diego. 

The yellow fever mosquito is typically a domestic species, found 
abundantly in towns. Like the Anopheles this mosquito is silent in its 
flight. It is said to be extremely wary. Howard observes that " it 
prefers the blood of white races to that of dark races, and attacks 
young, vigorous persons of fine skin and good color in preference to 
anaemic or aged people." 

Eggs. — The eggs of the yellow fever mosquito are deposited singly, 
are dark in color and each egg is surrounded by air cells (Fig. 82c). 
As in the Anopheles comparatively few eggs are deposited at one laying, 
i.e. from perhaps less than fifty to a hundred, and there may be 
several layings. 

1 Howard, L. 0., 1913. The Yellow Fever Mosquito, U. S. Dept. of Agric, 
Farmers' Bull. 547. 




analtu^: 



Fig. 86. — A mosquito larv: 
in classification named. 
J. B. Smith.) 



MOSQUITOES 



95 



• Hioratf 



Unlike the eggs of most species these can withstand desiccation to a 
very marked degree, some authors declaring that this is possible for 
several months. Ordinarily the eggs hatch in about forty-eight hours. 

Larvae. — The larvae are quite stalky, the breathing siphon is 
comparatively short and heavy (Fig. 856), and their position in the water 
is almost vertical, considerably more so than other Culicine species. 
The larval stage is ordinarily passed in about nine or ten days under 
average conditions. 

Pupae. — The pupae are characteristically Culicine; the breath- 
ing trumpets are, however, broadly triangular. Only about thirty-six 
hours is spent in this stage. 

Life History. — The yellow fever mosquito breeds by preference 
in artificial pools of rain water. (They are known, however, at times 
to breed naturally in brackish water.) Rain-water barrels, tanks, 
cisterns, tin cans, urns, etc. provide suitable places, also water collected 
between the leaves of certain members of the Agave family ; ornamental 
banana palms are often a great 
menace in this respect. ^---,-Jweatiung trumpets 

According to Howard the 
shortest period of development 
from egg to imago observed by 
Reed and Carroll in Cuba was 
nine and a half days, viz. : egg 
stage, two days ; larval stage, six 
days; pupal stage, thirty-six 
hours. From this very short 
period the time ranges from eleven 
to eighteen days according to the 
same author. 

Classification of Mosquitoes. 
— The principal characteristics on 
which the classification of mos- 
quitoes is based are indicated in Figs. 86, 87 and 88, together with 
the scale characteristics shown in Fig. 78 and wing venation shown in 
Fig. 71. 

The following key, adapted after Stephens and Christophers and 
Giles, according to Theobald, is not intended to be comprehensive and is 
only adapted for the purpose of this work. For a complete key including 
all known mosquitoes, the reader is referred to Theobald's Monograph 
of the Cidicidce of the World. 




...abdomen 



Swlmmerets 



Fig. 87. — A mosquito pupa with parts used 
in classification named. (Adapted after 
J. B. Smith.) 



Key for Classification of Mosquitoes 

Scutellum simple, never trilobed. Proboscis straight ; palpi long in male 

Anophelince 



and female 
AA. Scutellum trilobed 

a. Proboscis strongly recurved 



first submarginal 



cell very small 
MegarhininoB 



96 MEDICAL AND VETERINARY ENTOMOLOGY 



,»t&rsu$ 



taUncer 
fcasat segment 
o^ abdomen 







Fig. 88. 



.Ursa I Claws. 
onStit«iTs^ljo'v»it 

•An adult mosquito with certain parts used in classification Darned. (Adapted 
after J. B. Smith.) 



MOSQUITOES 97 

aa. Proboscis straight ; metanotum nude. 

1. Wings with six long scaled veins. 

2. Antennae with second joint normal in length. 

3. First submarginal cell as long or longer than posterior cell. 

4. Palpi of female shorter than proboscis, of the male long CulicincB 
4'. Palpi short in male and female Mdinos, 

Subfamily Anophelin^e 

Table of Genera 

First submarginal cell large 
I. Antennal segments without dense lateral scale tufts 

a. Thorax and abdomen with hair-like curved scales. Xo flat scales 

on head, but upright forked ones. 
Basal lobe of male genitalia of one segment 

1. Wing scales large, lanceolate . . Genus Anopheles Meigen 

2. Wing scales mostly small, long and narrow or slightly lanceolate 

Genus Myzomyia Blanchard 

3. Wings with patches of large inflated scales 

Genus Cycloleppteron Theobald 
Basal lobe of two segments 

4. Prothoracic lobes with dense outstanding scales 

Genus Feltinella n. g. 
Median area of head with some flat scales ; prothoracic lobes mam- 
millated 

5. Wing scales lanceolate . . . Genus Stethomyia Theobald 

b. Thorax with narrow curved scales ; abdomen hairy 

6. Wing scales small and lanceolate ; head with normal forked 

scales Genus Pyretophorus Blanchard 

7. Wing scales broad and lanceolate ; head with broad scales, not 

closely appressed but not forked or fimbriated 

Genus Myzorhynchella n. g. 

c. Thorax with hair-like curved scales and some narrow-curved ones 

in front ; abdomen with apical lateral scale tufts and scaly 
venter; no ventral tuft. 

8. Wing scales lanceolate . . . Genus Arribalzagia Theobald 

d. Thorax with hair-like curved scales; no lateral abdominal tufts; 

distinct apical ventral tuft. Palpi densely scaly. 

9. Wing with dense large lanceolate scales 

Genus Myzorhynchus Blanchard 

e. Thorax with hair-like curved scales and some narrow curved lateral 

ones ; abdomen hairy with dense long hair-like lateral apical 
scaly tufts. 

10. Wing scales short, dense, lanceolate ; fork cells short. 

Genus Christya Theobald 
/. Thorax with very long hair-like curved scales ; abdomen with hairs 
except last two segments which are scaly. Dense scale tufts 
to hind femora. 

11. Wings with broadish, blunt lanceolate scales 

Genus Lophoscelomyia Theobald 
g. Thorax and abdomen with scales 

12. Thoracic scales, narrow-curved or spindle-shaped ; abdominal 

scales as lateral tufts and small dorsal patches of flat scales 

Genus Nyssorhynchus Blanchard 

13. Abdomen nearly completely scaled with long irregular scales 

and with lateral tufts .... Genus Cellia Theobald 



98 MEDICAL AND VETERINARY ENTOMOLOGY 

14. Similar to above, but no lateral scale tufts Genus Neocellia, n. g. 

15. Abdomen completely scaled with large flat scales as in Culex 

Genus Aldrichia Theobald 

16. Thoracic scales hair-like, except a few narrow-curved ones in 

front ; abdominal scales long, broad and irregular 

Genus Kerteszia Theobald 
II. 17. Antennal segments with many dense scale tufts 

Genus Chagasia Cruz 
AA. 18. First submarginal cell, very small Genus Bironella Theobald 

Genus Anopheles 

Table of Species 

a. Wings spotted, legs unhanded, costa unspotted. 

1. A. maculipennis — Wing field four spots. Palpi unbanded. Europe, 
giving way to A. quadrimaculatus in North America. 

2. A. crucians — White spots on dark veins. Three dark spots on sixth 
vein. Tarsi unbanded ; palpi three white bands. North America. 

3. A. eiseni — Apical fourth of hind tibiae yellowish. Sixth vein wholly 
black. Guatemala. 

aa. Wings spotted, legs unbanded, costa spotted. 

4. A. punctipennis — Costa, characteristic yellow spot near apical fourth of 
wing fringe ; no spots. North America. 

5. A. pseudopunctipennis — Wings as in previous species but wing fringe 
with several yellow spots; (?) a distinct species. North America. 

6. A. franciscanus — Small species ; costa, a spot about middle, and a pure 
yellow apical spot; third vein white with two black spots. Fringe spotted. 
North America. 

aaa. Wings spotted, legs banded. 

7. A. gigas — Costa, two large costal spots. Legs with pale basal bands. 
A hill species. India. 

8. A. wellcomei — Costa, two small yellowish spots. Legs with narrow 
apical bands. Sudan. 

9. A. arabiensis — Costa, seven dark spots, four long and three short. 
Other veins much spotted. Fringe spots at all the vein junctions. Hind femur 
and tibia speckled — latter often has apical band. Palpi three white bands. 
Markings vary according to season. Arabia; 

10. A. dthali — Costa, four black spots, the basal the longest. First long 
vein four black spots, other veins pale. Wing fringe, no spots. Palpi, pale 
with two white bands. Arabia. 

aaaa. Wings unspotted, legs unbanded, thorax with abnormal pattern. 

11. A. corethroides — resembles A. bifurcatus, but differs in (a) thorax being 
pale brown with a large median anterior dark area, and a long lateral dark area 
behind, this as in Corethra. S. Queensland. 

12. A. bifurcatus — abdomen with golden hairs, thorax with two broad bare 
lines in front. Europe. 

13. A. algeriensis — abdomen with brown hairs, lateral scales of veins longer 
and finer than in A. bifurcatus. Anterior and posterior cross veins in same 
line in both sexes. In A. bifurcatus the posterior is internal in female, the 
anterior in male. Africa. 

14. A. barberi — differs from previous two in having stalk of first fork cell 
equal to instead of greater than one third length of cell. The larva lives in 
holes in trees. Maryland, U. S. A. 

aaaaa. Wings unspotted, legs unbanded, thorax with normal pattern, second 
fork cell exceeds half length of first, palpi banded. 



MOSQUITOES 99 

15. A. smithi — Wing scales very dense. Sierra Leone. 

16. A. nigripes — Not so dense as in previous species. Thorax, gray mark- 
ings. Europe, America. 

aaaaaa. Wings unspotted, legs unhanded, thorax with normal pattern, second 
fork cell does not exceed half the length of the first. 

17. A. aitkeni. Bombay presidency. 
aaaaaaa. Wings unspotted, legs banded. 

18. A. lindesayi — A dark species. Costa, black, apical white spot; hind 
femora with characteristic broad white band. Hill species chiefly. India. 

19. A. immaculatus — An ash-gray species. Slight apical bandings to tarsi. 
Palpi and proboscis lighter at apex. A very rare species. Ennur, Madras. 

Subfamily Megarhinin^e 
Table of Genera 

a. Palpi 5-jointed in female (long) Genus Megarhince 

b. Palpi 3-jointed in female (comparatively short) Genus Toxorhynchites 

Subfamily Culicin^e 
Table of Genera 

a. Legs more or less densely scaled. 

Posterior cross vein nearer the base than the mid cross vein ; hind legs with 
tarsi in male densely long scaled ; wing scales long and rather thick 

Genus Eretmapodites 

Cross vein as in Culex ; scales of crown and occiput broadly spindle-shaped ; 

3d long vein continued as distinct pseudovein into the basal cell 

Genus J anthinosoma 
Posterior cross vein nearer base of wing than mid cross vein ; wings with 

thin scales Genus Psorophora 

Posterior cross vein nearer apex of wing than mid cross vein ; wings with 

large pyriform parti-colored scales Genus Muscidus 

aa. Legs uniformly clothed with flat scales. 

Scales of the wings very large, flat, broad, asymmetrical Genus Panoplites 
Scales of wings dense, lateral ones large, elongated oval or lanceolate 

Genus Tceniorhynchus 
Metanotum nude, scales of wings much as in Tceniorhynchus, metanotum 
with a tuft of chetae and with patches of flat scales 

Genus Trichoprosopon 
b. Head and scutellar scales all flat and broad. 

Third long vein as an incrassation into the basal cell Genus Armigeres 
bb. Nape clothed with mixed narrow, curved, and upright forked scales, 
with small lateral patches of flat scales. 
Second antennal joint small or moderate-sized 

Scales of the wings small, lateral ones linear .... Genus Culex 
Second antennal joint very long, distal joints without scales 

Genus Deinokerides 
Second antennal joint very long, 2d to 5th joints clothed with scales 

Genus Brachiomyia 
Subfamily ^Edin^e 

Table of Genera 

A. Proboscis formed for piercing ; metanotum nude. 

a. Palpi three to five jointed. Body showing generally a distinct metallic 
luster. One or more of the legs provided with a paddle-shaped expan- 

H 



100 MEDICAL AND VETERINARY ENTOMOLOGY 

sion, formed of elongated scales, "3" nearer apex of wing than 
"4"; "2" nearer apex than "3"; III extended into basal cell 

Genus Sabethes 

b. Palpi two or three jointed ; non-metallic. 

Wing scales large and flat, and bracket-shaped; fork cells normal 

Genus JEdomyia 
Wing scales small, linear like Culex ; fork cells normal Genus JEdes 

c. Palpi five-jointed; fork cells normal; metallic Genus Hcemagogus 

d. Palpi two-jointed; fork cells very small; with metallic spots of flat 

scales on the thorax and elsewhere .... Genus Uranotcenia 

B. Proboscis formed for piercing ; metanotum armed with chetse : palpi small. 

Proboscis rather or very long Genus Wyeomyia 

A convenient key for the identification of eggs, larvae and pupae may be found 
in Mosquito Life by Mitchell, 1 pp. 216-258. 

1 Mitchell, Evelyn G., 1907. Mosquito Life. G. P. Putnam's Sons, N. Y., 
pp. xxii + 281. 



CHAPTER X 

MOSQUITOES AS DISEASE BEARERS 

A. Malaria 

Malaria. — Malaria is a widely distributed disease, prevalent to a 
greater or less degree on every continent. While not restricted to the 
lowlands, it does not occur extensively at high altitudes, primarily 
because of the lower temperature, i.e. the disease requires an average 
summer temperature of not less than 60° F. There are, however, 
situations in which it is known to occur at an elevation of 3000 feet, 
notably in Java and Madagascar. 

Malaria is also commonly known as ague, chills and fever, inter- 
mittent fever, remittent fever, jungle fever, paludism, etc. The 
symptoms, even though slight, are usually manifested in the form of a 
regularly appearing paroxysm consisting of three fairly well-defined 
stages, viz. : the cold stage (the chill) in which the skin becomes pale 
and has the appearance of " gooseflesh," the patient's teeth may chatter, 
and he may shiver more or less violently ; the next stage is the hot 
stage or fever, the temperature rising during the chill, the skin is hot and 
flushed ; the third stage is marked by the appearance of a general 
perspiration, the fever falls, and the patient becomes normal. The 
entire paroxysm may last but a few hours. In many cases the stages 
are not so well marked, neither do the paroxysms recur at exactly the 
same interval, — the latter depends largely on the type of infection. 

The disease is caused by blood-inhabiting Protozoa belonging 
to the genus Plasm odium. These parasites attack the red corpuscles, 
destroying the same while reproducing asexually; this asexual repro- 
duction or sporulation occurs at fairly regular intervals, i.e. twenty- 
four, forty-eight, or seventy-two hours, depending upon the species of 
Plasmodium involved, the paroxysm resulting at corresponding times. 
That the paroxysm is due not to the destruction of the myriads of cor- 
puscles at a given time, but to the liberation of a toxin produced by the 
intracorpuscular parasites, is now generally believed. 

Historical. — Malaria, though not receiving its name until the 
middle of the eighteenth century, has been known for many centuries, 
Hippocrates having divided periodic fevers into the quotidian (daily), 
tertian (every third day) and quartan (every fourth day). The fable 
of Hercules and the Hydra is believed to refer to malaria, and the 

101 



102 MEDICAL AND VETERINARY ENTOMOLOGY 

disease is mentioned in the Orphic poems. The successful treatment of 
malaria dates back previous to the seventeenth century. The Countess 
del Cinchon, the wife of the Viceroy of Peru, was cured of fever in 1638 
by the use of the bark from a certain tree. This bark was introduced 
into Europe in 1610, and in 1741 Linne named it "cinchona" in honor 
of the Countess del Cinchon. In 1753 Torti named the disease 
"malaria," believing it to be air borne and emanating from the bad air 
(mal aria) rising from swamps and marshes. 

The credit for the discovery of the causative organism belongs to 
Laveran, a French army surgeon who was stationed in Algeria. This 
discovery was made in 1880. Although the mosquito transmission 
theory is said to have been held for many years among the Italian and 
Tyrolese peasants and the natives of German East Africa, the first well 
formulated mosquito-malaria theory was advanced by King in 1883. 
In 1885 Golgi discovered that the periodicity of the fevers corresponded 
to the periodic sporulation of the Plasmodium. 

Nuttall (1899) refers to the interesting fact that the malaria-mos- 
quito theory has been repeatedly rediscovered by writers in various 
countries, e.g. Laveran first mentioned the theory in 1891, Koch (ac- 
cording to Pfeiffer) in 1892, Manson in 1894, Bignami and Mendini in 
1896 and Grassi in 1898. 

The greatest discovery in the history of malaria (as evidenced by the 
fact that two Nobel prizes have been awarded the discoverer) was made 
by the Englishman, Major Ronald Ross, in 1898, then stationed in India. 
Ross demonstrated beyond doubt the important role played by mos- 
quitoes in the transmission of malaria, and mankind owes no greater 
debt to a fellow man than this. Late in the same year Grassi proved 
that malaria can only be transmitted by a particular kind of mosquito, 
namely, Anopheles. 

In 1900, at the suggestion of Sir Patrick Manson, Doctors 
Sambon and Low built a mosquito-proof hut in the Roman 
Campagna, in which they lived during the most malarial months of 
that year without contracting malaria. At this time these investi- 
gators sent infected Anopheles mosquitoes from the Campagna to 
London, where Doctor Manson' s son, Dr. P. Thurburn Manson, and Mr. 
George Warren permitted themselves to be bitten by these mosquitoes 
and in due time became ill with the disease. 

The use of oil as a factor in mosquito control dates back to the 
beginning of the nineteenth century; however, the present extensive 
use of kerosene for this purpose is due largely to the efforts of Howard, 
beginning in 1892. 

While certain German investigators claimed to have reared the 
malaria parasite in vitro previously, it appears that the first recorded 
successful attempts to accomplish this were made by Bass in 1911. 

Circumstantial Evidence. — Immediately following great spring 
floods when the valleys become inundated and the receding water 



MOSQUITOES AS DISEASE BEARERS 103 

leaves behind it innumerable pools and overflowed cellars and cess- 
pools, there is always much more malaria than usual, a fact always 
predicted. Coincidentally mosquitoes are unusually abundant, and 
especially the noiseless kind. Exceedingly warm moist seasons always 
bring more malaria, while a prolonged drought is commonly said to 
kill the disease, as does the approach of cold weather. 

A very common suggestion made to escape malaria is to keep out 
of the " night air " and close windows and all openings which might per- 
mit the " night air " to enter. 

In localities where anti-mosquito campaigns have been waged with 
vigor there has quickly followed a decrease in malaria, no other pre- 
cautions having been taken. 

The circumstantial evidence against the mosquito (in a broad sense) 
may be summed up as follows : 

(1) Malaria exists endemically in districts where mosquitoes are 
present (all species except the Anophelines are eliminated experimen- 
tally) ; (2) malaria does not exist endemically where there are no 
mosquitoes (existing cases are without exception traced to an earlier 
visit on the part of the patient to some locality in which mosquitoes of 
the Anopheline type occur) ; (3) persons protecting themselves against 
mosquito bites while dwelling in malarial districts (otherwise living as 
do the natives) do not contract malaria ; (4) communities previously 
noted for malaria have been practically freed from this disease when 
efficient drainage (sewer) systems have been installed ; (5) properly 
conducted mosquito crusades result in the elimination of about 50 per 
cent of the cases of malaria within that district in the same season. (The 
existing cases can be accounted for through relapses and exposure to 
mosquito bites outside the protected district.) 

It may be said that malaria may be wholly absent in the presence 
of an abundance of mosquitoes. In answer to this it may be replied 
that there are several hundred species of mosquitoes, of which number 
only one or two species for any one locality are capable of transmitting 
malaria. Hence, first, the mosquitoes in such localities are probably 
all non-malaria-bearing, with the entire absence of the malaria-bear- 
ing species (Anopheline), or, secondly, if Anopheline mosquitoes are 
present, they have not become infected by the importation of persons 
affected with malaria, i.e. malaria must first be introduced before the 
Anopheline mosquitoes can carry it from person to person. 

Experimental Evidence. — The parasite of malaria can easily be 
seen by examining microscopically properly stained blood from infected 
persons. The disease can be produced experimentally in healthy 
persons by inoculation with parasitized blood taken from a malarial 
patient. 

Malaria is popularly believed to be present in certain sources of 
drinking water, also in overripe fruit. This was the case in two com- 
munities in California in which it was proposed to control the disease 



104 MEDICAL AND VETERINARY ENTOMOLOGY 

by combating mosquitoes. The sanitary inspectors drank this water, 
ate freely of the ripest fruit and were exposed to the severest heat of 
the day and remained free from malaria, having exercised the proper 
night precautions. That miasma from swamps has no direct relation 
to malaria was proved by Sambon and Low, as already noted. 

It is well known that blood taken directly from a patient suffering 
from malaria may show flagellated parasites. Ross, in 1895, in his 
Indian observations found these flagellated bodies in the intestines of 
mosquitoes which had fed on the blood of malarial patients. Many 
experiments were made and hundreds of mosquitoes examined during 
the next few years by Ross. The most striking condition found in some 
of these mosquitoes was the development of pigmented cells in the 
stomach wall, the pigment corresponding to malaria pigment Some of 
these mosquitoes gave positive results, while the majority gave nega- 
tive results. Those which furnished positive results were of a particu- 
lar species, and this gave the clew that the malaria parasite required a 
particular species of mosquito to serve as intermediary host. The con- 
nection between the flagellated bodies and the pigmented cells was fur- 
nished by MacCalluni in 1S9S. He found that the function of the 
flagellated cells was that of an impregnating body ; that each flagellum, 
of which there were several to each cell, impregnated a spherical para- 
site. MacC allium' s observations were made on the Proteosoma of birds, 
also known as " bird malaria."' Using the Proteosoma as a basis for 
his further observations. Ross found that the pigmented cells, migrating 
through the stomach wall of the mosquito x and encysting just beneath 
the peritoneal lining, grew steadily for three or four days, forming spindle- 
shaped bodies, which were shed into the body cavity and in six or seven 
days after feeding were found in vast numbers in the salivary glands. 

Grassi's experiments in the Roman Campagna and Sicily proved that 
human malaria was carried solely by Anopheline mosquitoes. Accord- 
ing to Nuttall one of the early experiments of Grassi and Bignami was 
conducted somewhat as follows : Three species of mosquitoes. Culex 
penicillaris, Culex malaria and Anopheles claoiger were collected in a 
malarial district, Maccarese, 22 miles from Rome. The insects were 
then allowed to bite a patient (who consented to the experiment ! in the 
Santo Spirito Hospital (Rome\ The patient had never had malaria. 
In addition to the bites from the imported insects the man was also 
subjected to the bites of mosquitoes emerging from larva? placed in the 
room occupied by him at night. A new supply of larva? was placed in 
the room every four to six days. In due time the man acquired aestivo- 
autumnal malaria as evidenced by the appearance of parasites in his 
blood. Grassi believed that the disease was due to the bites of Culex 
penicellaris because it was the most numerous, while Anopheles claviger 

1 It should he noted here that certain Culicine mosquitoes (Culex pipiefis) 
are the transmitters of Proteosoma though inefficient as transmitters of Plas- 
modium or human malaria. 



MOSQUITOES AS DISEASE BEARERS 105 

was present in very small numbers. Xuttall remarks that the infection 
could only have been produced by the latter, as has been determined 
since. 

After describing the conditions under which Sambon and Low lived 
in the Roman Campagna while experimenting with malaria, Manson x 
writes as follows : " Whilst this experiment was in progress mosquitoes 
fed in Rome on patients suffering from tertian malaria were forwarded 
in suitable cages to the London School of Tropical Medicine, and on 
their arrival were set to bite my son, the late Dr. P. Thurburn Manson, 
and Mr. George Warren. Shortly afterwards both of these gentlemen, 
neither of whom had been abroad or otherwise exposed to malarial 
influences, developed characteristic malarial fever, and malarial para- 
sites were found in abundance in their blood, both at that time and on 
the occurrence of the several relapses of malarial fever from which they 
subsequently suffered. The mosquito-malaria theory has now, there- 
fore, passed from the region of conjecture to that of fact." 

The Parasite. — The malarial parasites (Plasmodia) belong to the 
lowest forms of animal life, the Protozoa (Subphylum Sporozoa, Class 
Telosporida, Subclass Hsemosporida). The pigment of these red-blood- 
corpuscle-inhabiting parasites is dark and characteristic and properly 
termed melanin. The presence of the parasites usually gives rise to a 
periodic chill and fever, due to their periodic asexual reproduction 
(sporulation) and the liberation of a toxin in the human blood. 

To detect the presence of the parasite a drop of blood is drawn from 
the lobe of the patient's ear or finger tip, after proper cleansing with 
alcohol ; the droplet of blood is lightly touched with a glass microscopi- 
cal slide, upon which a film (smear) is made by gently and evenly spread- 
ing the droplet by means of a needle or edge of another slide. The film 
is then fixed and stained, using Romanowsky modifications, such as 
Wright and Leishman, also Giemsa and Jenner. If parasites are pres- 
ent in the blood, they should be visible after careful microscopical exam- 
ination as pigmented intracorpuscular bodies in the form of signet 
rings, amoeboid forms or as crescents in aestivo-autumnal fever of ten 
or more days' duration. Microscopic examination under an oil im- 
mersion lens is desirable, though crescents can easily be seen with lower 
powers. 

The ease with which parasites can be discovered in a blood smear 
depends on several important factors, — first, on the length of time that 
the patient has had malaria, and secondly on the condition that he has 
lately taken quinine when the chances for the discovery of parasites is 
reduced practically to nil. Ross 2 states that the parasites " will not 
generally be numerous enough to cause illness unless there is at least 

1 Manson, Sir Patrick, 1909. Tropical Diseases. Cassell and Company 
(London), pp. xx + 876. 

2 Ross, Ronald, 1910. The Prevention of Malaria. E. P. Dutton & Com- 
pany, Xe^v York. pp. xx + 668. 



106 MEDICAL AND VETERINARY ENTOMOLOGY 

one parasite to 100,000 hsematids ; that is, 50 parasites in 1 cmm. of 
blood; or 150,000,000 in a man 64 kilograms in weight. . . . Such 
calculations demonstrate the absurdity of supposing that there are no 
Plasmodia present in a person because we fail in finding one after a few 
minutes' search. As a matter of fact, even if as many as 150,000,000 
Plasmodia are present in an average man, the chances are that ten to fif- 
teen minutes' search will be required for each Plasmodium found ; while 
if we are careless or unfortunate, we may have to look much longer." 
The various types of malaria are due to the fact that there are 
several species of parasitic plasmodia, each of which produces specific 




Fig. 89. — To illustrate detection of malaria parasite, a. normal unparasitized red blood 
corpuscle ; b. young intracorpuscular parasite ; c. signet ring ; d. intracorpuscular cres- 
cent ; e. free female crescent ; /. free male or hyaline crescent ; g. female oval. 

symptoms. Three or possibly four distinct types are usually recog- 
nized : (1) Mstivo-autumnal or Malignant Tertian; (2) Tertian or 
Benign Tertian; (3) Quartan, and (4) Quotidian. 

a. Plasmodium precox Dofl. (H&mamceba prcecox Grassi et Fe- 
letti, Plasmodium falciparum Welch) is the cause of sestivo-autumnal 
fever (malignant tertian fever) of the tropics and subtropics with the 
paroxysm recurring every forty-eight hours. The pigment granules 
in this species are relatively few and very coarse. The infected red cor- 
puscle is usually normal in size, but may be slightly shrunken and 
crenated. The segmenting stage, which is rarely seen in the peripheral 
blood, is said to produce only from eight to ten merozoites, according to 
Stephens and Christophers, or from five to twenty-five and over accord- 



MOSQUITOES AS DISEASE BEARERS 



107 



ing to Deaderick. Characteristic crescents (Fig. 89) or gametocytes 
(immature sexual forms) are commonly observed in cases of ten or more 
days' duration. Crescents occur in this species only. The female cres- 
cents show the chromatin granules well concentrated in the mid-region, 
with slight stippling at both ends, while the male crescents have the 
chromatin thinly scattered with both ends hyaline (they are also called 
hyaline bodies or hyaline crescents). Certain relapses after months of 
latency are said to be traceable to a parthenogenetic cycle, in which the 
female crescents produce merozoites asexually, which now attack the red 
blood corpuscles, as do the ordinary sporulated forms. Sporulation 
occurs about every forty-eight hours. 

b. Plasmodium vivax Grassi et Feletti (Hcemamceba vivax Grassi et 
Feletti) is the cause of tertian fever or benign tertian malaria of temper- 



$Ste* 







it 










mmM& 



Fig. 90. — Signet ring stage of malaria parasite. 



ate climates, occurs also abundantly in the tropics and subtropics, 
with recurrent paroxysms regularly every forty-eight hours. In these 
parasites the pigment granules are very fine and are distributed through- 
out the red corpuscles as SchufTner's dots. The parasitized corpuscles 
are distinctly enlarged and are quite pale. The parasites are bizarre in 
form. There are no crescents in this species, and the gametocytes are 
not easily distinguishable from the asexual parasites, except for their 
more regular form and denser pigmentation. The number of elements 
in the sporulating or segmented stage commonly seen in the peripheral 
blood is larger than in the former, and their arrangement is irregular 
(fifteen or more, according to Stephens and Christophers) . Sporulation 
occurs regularly every forty-eight hours. 



108 MEDICAL AND VETERINARY ENTOMOLOGY 

c. Plasmodium malaria? Laveran (Laverania malaria? Grassi et 
Feletti, Hosmamoeba malarice Grassi et Feletti) is the cause of quartan 
fever, with recurrent paroxysms every seventy-two hours. This form 
of malaria is comparatively rare, and coincides in distribution with 
sestivo-autumnal fever. The pigment is coarse and generally occurs in 
marginal streaks or in bands. The parasitized corpuscles are usually 
normal in size, and the parasite is more or less oval in shape. The 
gametocytes are rarely seen. The segmenting stage gives rise to the 
typical " daisy " form, each sporulated body radiating from the center. 
The number of bodies varies from six to twelve, oftenest eight (Dea- 
derick). Sporulation occurs every seventy-two hours. 

d. Plasmodium falciparum quotidianum Craig is believed to be the 
causative organism of quotidian malaria, with paroxysms recurring every 
twenty-four hours. This must not be confused with multiple infec- 
tion on the part of other species of Plasmodia which might also result 
in daily paroxysms. This type of malaria occurs in practically all 
parts in which sestivo-autumnal fever occurs. The parasite resembles 
Plasmodium prwcox ( = P. falciparum) very closely, but the infected cor- 
puscles are said to be considerably smaller than normal, and are usually 
brassy in appearance. 

The signet ring (Fig. 90) is the earliest stage in the development of 
the intracorpuscular parasite of all species, and is characterized by a 
blue staining ring with a heavy chromatin dot (the nucleus) at or near 
the thinner segment. The thickness of the wider segment varies with 
the species, e.g. in the large conspicuous rings of both P. vivax and 
P. malaria?, the rings are quite thick and the dot is usually situated in 
a line with the thinner segment ; in P. precox the rings are smaller and 
thinner and the chromatin dot (commonly double) is frequently out of 
line with the ring. . There may be two and even three rings inside of one 
corpuscle. 

Life History of the Plasmodium. — The life history of malaria Plas- 
modia involves two distinct cycles ; namely, first, the asexual, also known 
as the human cycle, cycle of Golgi or schizogonic cycle ; and secondly, 
the sexual, also known as the mosquito cycle, cycle of Ross or sporogonic 
cycle. A third cycle which explains the recurrence of malaria after 
longer periods of latency is known as the parthenogenetic or virgin cycle, 
passed within the human body. 

The asexual cycle (Fig. 91, 1-6), passed within the blood of the 
human, begins with the introduction of spindle-shaped sporozoites in- 
jected into the circulation with the bite of the Anopheles mosquito. 
Each sporozoite not captured by phagocytes at once bores into a red 
cell, where it quickly goes into the signet ring stage, growing rapidly until 
the corpuscle is more or less filled depending upon the species of para- 
site, and is then known as a merocyte. The full-grown merocyte now 
divides into a larger or smaller number of bodies (also depending upon 
the species) which are then liberated, being now free in the plasma and 



MOSQUITOES AS DISEASE BEARERS 



109 




Fig. 91. — Diagram to show life history of parasite {Plasmodium prcecox) of aestivo-autumnal 
malaria. 1-6, asexual or schizogonic cycle in human blood, requiring 48 hours to com- 
plete (72 hours in quartan) ; 1, represents a vermicule or sporozoite, either in salivary 
gland of mosquito or newly injected into human circulation ; 2, represents a red blood 
corpuscle about to be parasitized by a sporozoite ; 3, shows a young parasite in signet 
ring form ; 4, fully grown parasite with dividing nucleus ; 5, shows parasite sporulated, 
but still intracorpuscular ; 6, sporulation, each body a merozoite ready to enter a new 
corpuscle ; some are sexual and may develop into gametes ; 7a, female gametocyte, still 
intracorpuscular ; 76, male gametocyte, also intracorpuscular ; 8a, free female crescent, 
which may sporulate, producing a parthenogenetic cycle (w, x, y, z) ; 8&, male gametocyte 
orjhyaline crescent (crescents do not ordinarily appear in the blood until ten days or more 
after infection) ; 9-20 illustrates the sporogonic or sexual cycle of the parasite within the 
body of a female Anopheline mosquito, requiring six to ten days and over to complete ; 
9a, 96, female and male gametocytes in stomach cavity of mosquito ; 10a, female gamete 
(macrogamete) ; 106, exflagellated male gametocyte; 11, deflagellated male gamete 
(microgamete) ; 12, fertilization ; (9-13 requires about 24 hours.) 13, ookinete or zygote 
ready to penetrate stomach ; 14, ookinete burrowing through stomach wall ; 15, ookinete 
outside of stomach wall and inside peritoneal lining, forming characteristic cyst, growing 
progressively larger. (16-19) in which the parasite sporulates, forming the sporozoites ; 
20 shows sporozoites (vermicules) escaping from cyst and migrating forward to salivary 
glands (21) ; (14-20 requires five'days or more.) 21, salivary glands of female mosquito ; 
22, head of female Anopheles. (Original, with suggestions from Grassi and Schaudinn 
in Mense's Handbuch.) 



110 MEDICAL AND VETERINARY ENTOMOLOGY 

are known as merozoites. The time required for this sporulation is from 
twenty-four to seventy-two hours according to the species. Each mero- 
zoite now enters another adjacent red cell and again the cycle repeats 
until the infection is great enough to produce a paroxysm, i.e. in from 
six to twelve days, commonly about ten days. 

The great majority of the merozoites are asexual, but some of them 
are potential males and females, which require a longer time, probably 
not less than ten days, to develop to their full growth, then known as 
gametocytes. In Plasmodium viva.v, the sexual forms are not easily recog- 
nized ; however, the following characters are useful : " (1) their larger 
size, (2) more abundant pigment, (3) there is usually only one fairly large 
chromatin mass, whereas in an asexual form of nearly equal size the 
chromatin has already begun to divide into several portions (segment- 
ing stage) " (Stephens and Christophers). In P. praeco.r the sexual 
individuals are in the form of crescents. The female crescent (macro- 
gametocyte) has the pigment collected at the center (Fig. 89e), while the 
male crescent (microgametoeyte) has the pigment scattered throughout 
and is known as a hyaline crescent (Fig. 89/). 

With the complete development of the gametocytes all is ready for 
the next cycle (the sexual) which can only be undergone within the body 
of an Anopheline mosquito. In the meantime the asexual cycle is 
repeated over and over, unless quinine is taken to destroy the parasites, 
or until senescence occurs. The gametocytes are not thus easily de- 
stroyed, persisting in the body for long periods of time, and may, under 
certain conditions, result in relapses, without reinfection by mosquitoes, 
which relapse is traceable to a parthenogenetic cycle of the female 
(Fig. 91 ic, x, y, z). But for this phenomenon, which may, of course, 
fail to occur, a person eventually becomes rid of malaria, provided he 
avoids reinfection by mosquitoes through removal from a malarial lo- 
cality, because of the senescence which naturally results from continued 
sporulation without sexual intervention or rejuvenation in the mosquito. 
It is believed that this senescence or eventual dying off of the non-sexual 
forms is due to the toxin produced by these organisms reacting upon 
themselves. 

Hence it becomes clear that the sexual cycle is necessary to the life 
of the species. It is a well-known fact that the male garnet ocyte extrudes 
flagella when malarial blood is exposed to the air, as when in contact 
with a glass slide. The parasites when thus taken from their normal 
habitat invariably die within a few minutes, unless a special medium 
is employed; e.g. that devised by Bass in which the asexual cycle 
may be observed outside the human body. 

Sexual development, the cycle of Ross (Fig. 91, 9-22) has only 
been observed in the female Anopheline mosquito ; in the stomach of 
this insect flagellation of the male gametocyte takes place. After a 
peripheral arrangement of the chromatin (in clumps corresponding to 
the number of flagella) there are extruded from three to six long slender 



MOSQUITOES AS DISEASE BEARERS 111 

filaments (flagella), each of which breaks loose from the parent body 
(exflagellation), forming the male gamete {microgamete) corresponding 
in function to the spermatozoon of higher animals. The female game- 
tocyte, now known as the macrogamete, having been taken into the stom- 
ach of the mosquito with the microgametocytes in the act of sucking 
blood, now also undergoes certain changes, becoming rounded or oval 
in form with the chromatin mass centrally located. In this condition, 
still in the stomach of the mosquito, the microgamete penetrates, i.e. 
fertilizes the macrogamete, producing the ookinete, in which stage the 
wall of the stomach is penetrated and a position is taken up just beneath 
the membrane forming the outer stomach lining. In this position the 
parasite grows enormously, forming a cyst (Fig. 91, 15-19) in which many 
nuclei appear in from four to five days. These tiny nucleated bodies 
give rise to hundreds of spindle-shaped organisms (sporozoites) which are 
in from twenty-four to forty-eight hours more shed into the body cavity 
of the mosquito. The sporozoites eventually collect in the salivary 
glands, remaining there until the mosquito bites again, when many of 
them may be injected with the saliva into the wound. The time re- 
quired for the completion of the sexual cycle varies from seven to ten 
days under favorable conditions, i.e. an average temperature of not less 
than 60° F. Once infected the mosquito probably remains infected for 
the rest of its life. 

With the introduction of the sporozoites into the blood of the next 
victim the asexual cycle begins as already explained. 

Time Factor. — Although there are some localities in which nearly 
all the inhabitants are infected with malaria, newcomers or visitors may 
or may not soon fall a prey to the disease, for the reason that not more 
than 25 to 35 per cent of the Anopheles mosquitoes are infected during 
the height of the season and correspondingly fewer early in the spring. 
This is dependent upon both the time when the infected person and the 
next victim are bitten. Obviously the mosquito cannot transmit malaria 
when there is none present to be transmitted ; again, the sexual parasites 
(gametocytes) must be in the peripheral circulation when the mosquito 
bites the infected individual ; and again after the mosquito becomes in- 
fected a period of not less than six days (possibly five in benign tertian, 
and twelve days in sestivo-autumnal) must elapse before a new victim 
can be inoculated, i.e. the time required for the sexual development of 
the parasite. This incubation period may be prolonged through reduced 
temperature, with apparently no development in low temperatures 
(according to Manson this phase of the malaria parasite requires a 
" sustained average temperature of at least 60° F.")- Thus it becomes 
evident that the time factor plays an important role in the spread of 
malaria. 

Is Malaria Inherited by Mosquitoes ? — For the reason that malaria 
is said at times to be contracted by explorers who have entered unin- 
habited territory it is believed by some that the mosquitoes of said ter- 



112 MEDICAL AND VETERINARY ENTOMOLOGY 

ritory had become infected perhaps years ago and that the parasite has 
been handed down from generation to generation from the female to the 
ovum, ovum to larva and thus through the mosquito cycle. The fact 
that Texas fever is thus inherited and infection is brought about by the 
seed tick seems to lend weight to the argument. To test this matter 
larvse of Anopheles quadrimaculatus were brought by the writer from an 
intensely malarial district to Berkeley and the adults reared from these 
were permitted to bite healthy students, and in no case did infection 
result. 

Knowing the life history of the parasite it would be more reasonable 
to assume that other warm-blooded animals besides man harbor the 
protozoon during its asexual cycle, but numerous and convincing 
experiments, in which monkeys, horses, dogs, cats, rabbits, pigeons, 
owls, etc., also frogs and turtles were used, negate this assumption. 

The explanation is probably to be found in the fact that such indi- 
viduals must necessarily pass through malarial districts while on their 
way to uninhabited territory. Infection might easily result, but the 
malaria symptoms do not appear until the destination is reached. The 
time factor and exposure, no doubt, explain the phenomenon. 

Anopheline Species Concerned. — Although no Anopheline mosquito 
should be trusted, there are comparatively few species which are experi- 
mentally known to be carriers of malaria. Anopheles quadrimaculatus 
Say and A. crucians Wied. are the most dangerous North American 
species. While A. punctipennis Say may be very abundant in certain 
localities, malaria may be rare or absent. Anopheles maculipennis 
Meig. is the most important European species; A. albimanus Wied. 
and A. (Cellia) argyrotarsis Rob. are the most important species for 
Central America. Moreover it has been found that not all species of 
malaria parasites can be carried equally well by the same species of 
Anopheles, e.g. A. crucians is said to be the most important carrier of 
sestivo-autumnal fever but is negative to other forms. 

Several other genera of Anopheline mosquitoes (Asiatic and African) 
include malaria-bearing species, among them Cellia, Nyssorhynchus, 
e.g. N. fuliginosus Giles of India and the Philippines, Myzorhynchus, 
e.g. M. sinensis, Wied. of China and the Philippines, and Myzomyia, 
e.g. Myzomyia minimus Theo. of the Philippines. The aforementioned 
genera are all to be included in the genus Anopheles. 

How Does the Malaria Parasite Overwinter ? — Since malaria has 
a typical seasonal occurrence, with little or no appearance during the 
winter months, the question arises, does the parasite overwinter in its 
human host to break out in the spring in individual cases by the process 
of parthenogenesis, or does it overwinter in the body of the mosquito ? 
The weight of evidence is against the latter possibility. The writer 
believes that the Anopheles mosquito seldom or ever takes a suck of 
blood before going into hibernation. A suck of blood would militate 
against the life of the mosquito inasmuch as it causes the development 



MOSQUITOES AS DISEASE BEARERS 113 

and ultimate extrusion of ova and that terminates the life of the insect. 
Other physiological reasons involving further increased metabolism seem 
to discount the possibility of successful hibernation. Furthermore the 
writer has seen great numbers of voracious Anopheles in the spring both 
indoors and out, and has been frequently bitten by these as have many 
others without becoming infected. These hibernated individuals on 
coming out early in the spring bite viciously even at noonday. Further- 
more evidence that infected mosquitoes exist during the winter months 
seems to be lacking or has been overlooked. 

On the other hand latent human infection has been amply proved and 
this may easily lead to the infection of the mosquitoes appearing in the 
early spring and thus lead to the spread of malaria as the season advances. 

B. Yellow Fever 

Yellow Fever. — : Yellow fever is a disease peculiarly restricted to the 
tropics, being endemic in the West Indies, spreading thence northward 
into the southern United States and westward into Panama, central 
America, Mexico, the west coast of South America and parts of Africa. 
The disease is marked by a rapidly increasing fever, headache and back- 
ache, and in most cases followed in three or four days by a yellow color- 
ing of the skin (whence the specific name) and a characteristic black 
vomit. 

A Mosquito the Carrier. — Finlay of Havana in 1881 was the first 
to advance the mosquito transmission theory, though Nott (according 
to Nuttall) as early as 1848 attributed it to the higher insects. Though 
the former carried on what is now known to have been incriminating 
experiments with mosquitoes on non-immunes, his theory was discredited, 
until Sternberg, Surgeon General of the United States Army, became 
interested in his (Finlay's) theory, made stronger through the malaria 
discoveries, and established a commission in 1900 to study the yellow- 
fever-mosquito theory in Cuba. The commission consisted of Doctors 
Walter Reed, James Carroll, Jesse W. Lazear and Aristides Agramonte, 
and of these Doctors Carroll and Lazear contracted the disease during 
the progress of the investigation, the latter succumbing to the attack. 
In the autumn a field station was established named Camp Lazear in 
honor of the deceased investigator. The camp was systematically 
arranged for the most accurate observations and experiments. Two 
small buildings were erected, one of which was used to determine whether 
yellow fever can be transmitted through contact with soiled articles of 
dress and bedding, ventilation being purposely poorly provided for, the 
only precaution being the exclusion of mosquitoes. The second building 
consisted of two rooms, with thorough ventilation and disinfection ; one 
room was kept free from mosquitoes, while into the other were intro- 
duced mosquitoes which had previously bitten yellow fever patients. In 
all cases the individuals experimented on were non-immunes. In the 



114 MEDICAL AND VETERINARY ENTOMOLOGY 

first case, those exposed to fomites, none became infected, though the 
experiment lasted over two months. In the second case, those indi- 
viduals occupying the mosquito-protected room did not become diseased, 
while six out of the seven occupying the room into which mosquitoes were 
introduced became ill with yellow fever. The following conclusions were 
reached by the commission : 

" 1. The mosquito — C.fasciatus (later known as Stegomyia calopus, 
now M&es calopus) serves as the intermediary host for the parasite of 
yellow fever. 

2. Yellow fever is transmitted to the non-immune individual by 
means of the bite of the mosquito that has previously fed on the blood 
of those sick with this disease. 

3. An interval of about twelve days or more after contamination 
appears to be necessary before the mosquito is capable of conveying the 
infection. 

4. The bite of the mosquito at an earlier period after contamina- 
tion does not appear to confer any immunity against a subsequent 
attack. 

5. Yellow fever can also be experimentally produced by the sub- 
cutaneous injection of blood taken from the general circulation during 
the first and second days of this disease. 

6. An attack of yellow fever, produced by the bite of the mosquito, 
confers immunity against the subsequent injection of the blood of an 
individual suffering from the non-experimental form of this disease. 

7. The period of incubation in thirteen cases of experimental yellow 
fever has varied from forty-one hours to five days and seventeen hours. 

8. Yellow fever is not conveyed by fomites, and hence disinfection 
of articles of clothing, bedding, or merchandise, supposedly contami- 
nated by contact with those sick with this disease, is unnecessary. 

9. A house may be said to be infected with yellow fever only when 
there are present within its walls contaminated mosquitoes capable of 
conveying the parasite of this disease. 

10. The spread of yellow fever can be most effectively controlled by 
measures directed to the destruction of mosquitoes and the protection 
of the sick against the bites of these insects. 

11. While the mode of propagation of yellow fever has now been 
definitely determined, the specific cause of this disease remains to be 
disco vered." 

Etiology. — The work of the Yellow Fever Commission proved 
beyond doubt that the causative agent of yellow fever is blood inhabit- 
ing, is a filterable virus and is not traceable to Bacillus icteroides of 
Sanarelli (1897). The behavior of the disease indicates that it is of 
protozoal nature, perhaps closely related to malaria, but all careful 
research thus far put forth has failed to reveal an organism. Seidelin 
(1909) believed it to be Paraplasma flavigenum, but this is strongly 
denied by other workers. 



MOSQUITOES AS DISEASE BEARERS 



115 



Time Factor. — Since the yellow fever mosquito is both diurnal and 
nocturnal early in its adult history, it seems that the virus could be 
conveyed at any time of the day or night ; this is, however, not true, as 
evidenced by the following observations : first, a lapse of at least twelve 
days is required before the bite of the mosquito becomes infective; 
second, after once having fed and deposited her eggs (three days later) 
the mosquito becomes nocturnal in habit. Therefore the day-flying 
individuals are too young to harbor the infective virus of yellow fever. 

Another important factor to be considered is that the Stegomyia can 
only become infected by feeding on a Yellow Fever patient during the 
first three days of his sickness. 

As in malaria, infective blood from a yellow fever patient loses its 
virulence on exposure to air, — " virulent blood serum lost its virulence 
in forty-eight hours, if exposed to the air at 24° to 30° C." (Mar- 
choux and Simond). 

C. Filariasis 

Filariasis. — Filariasis is a disease of the lymphatic system pro- 
duced by nematode worms of the genus Filaria. It is manifested by a 
swelling, often to enormous pro- 
portions, of the lower extrem- 
ities, commonly the scrotum. 
In its more pronounced and 
advanced stages it commonly 
causes elephantiasis, although 
in this stage the filarial may 
not be present. 

Filariasis and elephantiasis 
are comparatively common in 
the tropics and occur also in 
certain subtropical regions ; ac- 
cording to Manson * about every 
second individual in Samoa is 
thus afflicted. 

While the absence of spe- 
cific filarial poisons, which might 
produce the disease, has not 
been disproven, it is said that the swellings are produced by occlusion 
of the lymphatics on the part of the nematodes. 

The Parasite. — Although there are several blood-inhabiting worms 
belonging to the family Filariidse, only one species seems to be of any 
great pathological importance, namely Microfilaria bancrofti Cobbold 
{Filaria sanguinis hominis Lewis), a tropical and subtropical species. 

Microfilaria bancrofti, which is the larval form of Filaria bancrofti, 
inhabits the blood plasma, is a very slender worm, about the diameter 

1 Manson, Sir Patrick, 1909 (loc. cit.). 




Fig. 92. 



Microfilaria bancrofti, in human blood. 
X 333. 



116 MEDICAL AND VETERINARY ENTOMOLOGY 

of a red blood corpuscle and is about .3 mm. in length (Fig. 92). It is 
inclosed in a very delicate sheath inside of which the worm has some 
latitude of motion both forward and backward. It is known that this 
parasite maintains a very striking periodicity, being abundant in the 
peripheral circulation only at night, beginning with the early evening 
and lasting until early morning with the greatest abundance at mid- 
night, at which time Manson reports that "it is no unusual thing to 
find as many as three hundred, or even six hundred in every drop of 
blood." During the day filariae are found in the lungs and large 
visceral blood vessels. 

The adult filariae, which are slender hair-like worms, inhabit the 
lymphatic ducts. The female parasite measures from 85 to 90 mm. in 
length and the male about 40 mm. (Manson). The ovo viviparous 
females extrude myriads of larval filariae into the lymph sinuses which 
shortly thereafter swarm into the blood vessels, occupying the lungs 
mainly during the day and the peripheral vessels by night. 

The Mosquito's Role in Filariasis. — Manifestly the swarming of 
thousands upon thousands of Microfilariae in the peripheral blood at 
night offers the very best opportunity for passage into the body of noc- 
turnal blood-sucking insects, of which the mosquito stands the best 
chance, owing to relative abundance and habits. The Culicine mosqui- 
toes for some reason seem to be the most important instruments of 
transmission, particularly Culex (fatigans) quinquefasciatus Say. 

Once the Microfilariae are in the stomach of the mosquito these burst 
themselves free from their enclosing sheaths and proceed to migrate to 
the thoracic muscles, where a definite metamorphosis is undergone, 
resulting in a great increase in size, and the formation of a mouth and 
alimentary tract (Manson). This metamorphosis requires from sixteen 
to twenty days, depending on the temperature as do other mosquito- 
borne parasites. From this position the worms work their way into 
the ventral portions of the head and the proboscis inside the labium. 
From this point they enter the wound produced when the mosquito 
pierces the skin of its victim. Apparently the filariae burrow directly 
through the membranous portion of the labella at the point of attach- 
ment to the labium. From the peripheral system the nematodes soon 
find their way into the lymphatics where sexual maturity occurs. 

Culex (fatigans Wiedem.) quinquefasciatus Say is one of the 
most abundant and widely distributed species of Culicine mosquitoes 
of the tropics and subtropics. It is a comparatively small species 
(about 5 mm.) and is uniformly brown, varying from light to dark, in 
color. On the thorax there are situated two narrow median indistinct 
longitudinal lines. Apparently any stagnant fresh water, from the 
clearest to the vilest, affords a good breeding place for Culex quinque- 
fasciatus. Stagnant, filthy gutter water seems to be especially favorable. 

The entire life history, from egg to imago, is completed in about ten 
days under optimum conditions. 



MOSQUITOES AS DISEASE BEARERS 117 



D. Dengue 

Dengue, or Breakbone Fever, an epidemic, infectious, influenza-like 
disease of the tropics and subtropics, breaks out suddenly as an acute 
fever with " eruption and peculiarly severe rheumatic-like pains in the 
joints and limbs . . . not accompanied by pulmonary and other serious 
complications " (Manson). The disease is benign and of short duration. 

It is caused by a filterable virus which is blood-inhabiting like yel- 
low fever. The incubation period is said to be from two to five days. 

How Transmitted. — Sufficient evidence, both experimental and 
circumstantial, is at hand to incriminate mosquitoes, notably Culex 
quinquefasciatus and M&es calopus ; and at least one reputable phy- 
sician has told the writer that the control of mosquitoes during a cer- 
tain dengue epidemic in the Philippines resulted in the control of the 
disease. Whether or not there were other factors of importance in- 
volved is, of course, a question. 

E. Verruga 

Verruga {Verruca peruana), Carrion's disease or oroya fever, 
occurs endemically in certain high altitudes in Peru. According to 
Giltner l the disease is characterized by fever, rheumatoid pains, anaemia 
and an eruption which develops into bleeding, warty tumors. It is an 
infectious disease of ancient origin attacking persons of both sexes and 
all ages. The mortality is very high in the malignant form, while in the 
benign form the mortality is low. The incubation period is from 
one to three weeks. 

Causative Organism. — The causative organism of verruga has not 
been discovered ; however, characteristic intracorpuscular bodies are 
present, at first believed to be parasites, and so described in the Verruga 
Expedition Report. 2 These bodies are known as " Bartonia bodies," 
or X-bodies, and are described as follows : 

" Bartonia bacilliformis . Gen. et sp. no v. Parasites consisting of 
rounded or oval forms or of slender straight, curved or bent rods occur- 
ring either singly or in groups, but characteristically in chains of several 
segmenting organisms, sometimes swollen at one or both ends and fre- 
quently beaded. Reproduction occurs by binary division. Endowed 
with independent motility, moving in the direction of the long diameter, 
living within the red blood corpuscles of man and producing a grave 
form of anaemia known in Peru as Oroya fever. Stained preparations 
suggest differentiation of cytoplasm and nuclear material." 

1 Giltner, H. A., 1911. Verruca peruana or Carrion's disease. Journ. 
Amer. Med. Assoc, Dec. 23, 1911. 

2 Strong, R. P., Tyzzer, E. E., Brues, Charles T., Sellards, A. W., Gastiaburn, 
J. C, 1913. Verruga peruviana, Oroya fever and Uta, preliminary report of 
the first expedition to South America from the department of Tropical Medi- 
cine of Harvard University. Journ. Amer. Med. Asso., Vol. LXI, No. 19. 



118 MEDICAL AND VETERINARY ENTOMOLOGY 

Mode of Transmission. — The first experimental transmission of 
verruga was accomplished by Townsend x in Peru, the agent having 
been Phlebotomus verrucarum (Townsend) and the animal experimented 
on was a hairless dog. The incubation period in this animal was about 
six days, i.e. on July 11, 1913, 1 cc. " of artificial serum containing the 
triturated bodies of twenty females of the Phlebotomus, collected on the 
night of July 9-10 in Verruga Canyon " was injected subcutaneously 







) / 




* 


\lvB 


I 


• : JP 












T 







Fig. 93. — Phlebotomus or sand fly (male, left ; female, right) . Carrier of three-day fever. 

— ios (rnnamif T*anci \\o\ fovor anr] Vprrn as X 8. 



ebotomus or sand fly (male, left ; female, right). Ci 
Other species transmit Papatici fever and Verruga. 



in the right shoulder of the dog, and on July 17 the typical eruption be- 
gan to appear. 

The same author 2 later reports a human case in which the infec- 
tion was undoubtedly introduced by the bites of Phlebotomus (" fifty- 
five unmistakable Phlebotomus bites on the backs of his hands and 
wrists ") received September 17, 1913, X-bodies appearing October 1, 
but " no clinical symptoms other than a headache or slight feverishness 
at times, until October 25, when a decided rise of temperature occurred 
and the X-bodies were found to be much increased in number/' 

Phlebotomus Flies. — The Phlebotomus flies (Fig. 93) belong to the 
family Psychodidse of the order Diptera, commonly known as " owl 

1 Townsend, Charles H. T., 1913. The Transmission of Verruga by Phle- 
botomus. Journ. Amer. Med. Assoc, Vol. XIV, No. 19. 

2 Townsend, Charles H. T., 1913. Human case of Verruga directly trace- 
able to Phlebotomus verrucarum. Entomological News, Vol. XXV, No. 1. 



MOSQUITOES AS DISEASE BEARERS 119 

midges," thickly haired moth-like flies of small size (3-4 mm. long). 
The wings are ovate in shape with heavy, almost exclusively longitudi- 
nal veins. The wings are densely hairy and fold roof-like over the 
abdomen. The habits of the Phlebotomus flies are described by several 
authors, among them Townsend, 1 who says that the tiny blood-sucking 
gnats " avoid wind and sun and full daylight. They appear only after 
sunset, and only then in the absence of wind. They enter dwellings if 
not too brightly lighted, but are not natural frequenters of human 
habitations. They breed in caves, rock interstices, stone embankments, 
walls, even in excavated rock and earth materials. . . . They hide by 
day in similar places or in shelter of rank vegetation. Deep canyons, 
free from wind and dimly lighted, are especially adapted to them. Thick 
vegetation protects them from what wind there is by day or night. 
. . . The flies suck the blood of almost any warm-blooded animal, and 
even that of lizards in at least one known case. Thus they are quite 
independent of man, and this accords with the verruga reservoir being 
located in the native fauna." 

The life history of Phlebotomus papatasii (related to " Papatici 
Fever," a benign dengue-like disease) is said by Marett 2 to require 
about three months, — egg stage, six to nine days ; larval stage, about 
eight weeks ; and pupal stage, from eleven to sixteen days. 

Marett also suggests the following prophylactic measures, viz. : 
" facing of walls, the removal of heaps of stones and the blocking of all 
holes which might serve as shelter places for the flies ; also covering the 
ventilators with fine-meshed wire gauze, and the cleaning o: all rough, 
made ground from weeds, so that all holes may be discovered and filled 
up with beaten earth. The encouragement of gardening on such grounds 
is, he thinks, also desirable. Large embankments should be planted 
with native aromatic plants such as thyme, pennyroyal, etc., and kept 
well earthed." 

1 To-wnsend, Charles H. T., 1913. A Phlebotomus, the practically certain 
carrier of verruga. Science, N. S., Vol. XXXVIII, No. 971. 

2 Marett, Capt. P. J., 1913. The Phlebotomus Flies of the Maltese 
Islands. R. A. M. C. Journ. XX, Xo. 2, pp. 162-171. (Abstract in The 
Review of Applied Entomology, Vol. 1, Ser. B. Part 2, pp. 27-29.) 



CHAPTER XI 
MOSQUITO CONTROL 

Where Mosquitoes Breed. — As has already been pointed out, water 
is absolutely essential for mosquito breeding, though the situation varies 
somewhat for the species. Places suitable for Culicine mosquitoes are 
not always suitable for the Anopheles, but generally where the latter is 
found the former may also occur. The Culicine female will deposit her 
eggs even in the smallest receptacles containing water, such as broken 
gourds, tin cans, tubs, barrels, etc. (Fig. 94). It should be noted here 




Fig. 94. 



Tin cans, tubs and barrels in which water may stand and breed mosquitoes. 



that running water is not a favorable breeding place for several obvious 
reasons illustrated in the life history already discussed. However, a 
running stream should be " edged up " so that no little coves are formed 
in which the water remains comparatively quiet. This applies also to 
gutters (Fig. 95) and irrigation ditches. 

The most favorable places for the propagation of Anopheles are 
overflowed areas in which the water is shallow enough to allow grass and 
other low vegetation to be barely covered or slightly protruding (Fig. 
96) ; such conditions are often produced by breaks in irrigation ditches, 
leaking water supply pipes, " leaky " hydrants (Fig. 97) and improperly 
channeled creeks. Marshy areas, in which the water is just below the 
surface, are made dangerous through the hoof marks of cattle and horses 
The writer has found that places, which the casual observer considers 
highly dangerous, are often quite harmless. Reservoirs, dredger ponds, 
and sluggish streams are often regarded with the keenest disfavor, 
though examination may indicate the entire absence of larvae. A 
badly kept basin or reservoir may, however, prove a menace due to the 

120 



MOSQUITO CONTROL 



121 



growth of vegetation along the edges and to the shallow condition of the 

water. A clean pond with sharp, deeply cut banks need not be a menace 

as a mosquito breeder, 

especially when stocked 

with surface-feeding 

fishes. 

A receding stream 
(Fig. 98) often leaves 
shallow ponds along its 
banks. These very fre- 
quently become most 
suitable breeding places 
for mosquitoes, especially 
Anopheles. The con- 
struction of railroads and 
highways frequently 
results in obstructing 
natural drainage, thus 
causing water to stand. 

It would hardly seem 
possible for wrigglers to 
develop in soap and lye 
laden pools from laun- 
dries, but such is never- 
theless frequently the 
case, even for Anopheles. 
Cesspools also often 
prove a serious menace. 

Essentials of Control. 
— In our study of the 
life history of the mos- 
quito we have seen that 
standing water (or at 
least very sluggish water) 
is absolutely necessary 
for the propagation of 
mosquitoes; therefore, the essentials of control are at once evident, 
namely, the drainage of the water or its protection mechanically to 
prevent the adult female from depositing her eggs thereon or the appli- 
cation of chemicals to destroy the larva? and pupse. Manifestly this 
calls for either temporary or permanent control. Temporary control 
consists in the application of some insecticide to the water, such as 
kerosene, nicotine, phinotas oil or salt (in the case of fresh-water species 
under certain conditions) . This method requires more or less constant 
repetition, and involves repeated expenditure of time, labor and money, 
but is extremely useful and really essential during the time that the per- 




Fig. 95. — Stagnant water in gutters breeds numerous 
mosquitoes, often Anopheles. 



122 MEDICAL AND VETERINARY ENTOMOLOGY 



manent work is being advanced, in that wrigglers and tumblers, which 
have already made their appearance, are destroyed. 

For the permanent control of mosquitoes, especially the Anopheles, 
the best method, by all odds, is drainage, correction of irrigation defects, 
cutting deeper channels where the water spreads, etc. Thirty minutes' 
labor in cutting a ditch deeper, or digging a new one for a short distance, 

has very often elim- 
inated a nuisance that 
has bred malaria mos- 
quitoes season after 
season. 

It is highly im- 
portant that control 
efforts should be sys- 
tematic and thorough. 
Haphazard, slipshod 
work only results in dis- 
satisfaction and new 
crops of mosquitoes. 
Oiling Methods. 
— As has already 
been explained, mos- 
quito wrigglers and 
tumblers must come 
to the surface of the 
water for air, hence 
any material that will 
form an effective film 
over the surface of the 
water will serve to 
suffocate them. For 
this purpose kerosene 
has been found to be 
the cheapest and at 
the same time most available material. After a coat of oil has been ap- 
plied the previously disturbed wrigglers and tumblers may be seen to rise 
and touch the under side of the oil film and successively try place after 
place for a point of emergence. Death from suffocation follows in from 
three to fifteen minutes. The same results can be secured by placing 
wrigglers and tumblers in a vessel of water and agitating violently for a 
few minutes so that the insects cannot come to the surface to breathe. 
Kind of Oil. — The most desirable oil for mosquito control is one 
that will spread most readily without breaking up into patches and that 
will remain on the water for the longest time in an effective condition. 
Crude oil, it will be seen, breaks up into patches between which the water 
is not affected. Wrigglers have been found by the writer developing in 




Fig. 9b. — An ideal Anopheles breeding place. The water 
is shallow and clear, with much vegetation. Also 
shows use of knapsack spray pump. 



MOSQUITO CONTROL 



123 



such situations in localities where oil had been applied liberally. Sev- 
eral very prominent fiascos have been made in attempting thus to 
control mosquitoes. Crude oil furthermore cannot be used well in ordi- 
nary spray pumps. The lasting quality is, however, very good. Kero- 
sene spreads most satisfactorily and does its work quickly, but evaporates 
in a comparatively short time, thus requiring frequent repetition. A 
mixture of the two can very well be made which will bring about 
more nearly the desired results. Our best results have been obtained 
with a mixture of approximately 
equal parts of crude oil and kero- 
sene, though the proportion may per- 
haps safely range to three parts of 
the former to one of the latter. We 
have also used successfully a treated 
stove oil of about 28° Beaume. 

Oil purchased on the market as 
" crude oil " varies from 12° to 18° 
Beaume, while " stove distillate " 
varies from 28° to 32°, and water- 
white kerosene from 40° to 42°. 
Knowing the specific gravity of the 
oil purchased, it can easily be cal- 
culated how to mix with lighter or 
heavier oil in order to obtain the 
required consistency. Thus if 
kerosene (42°) is at hand and crude 
oil (15°), use about ten gallons of the 
former to twelve gallons of the latter. 
For spring and autumn, 28° to 30° 
Beaume is to be recommended, 
while for summer use a heavier oil 
at about 26° is preferable. To mix 
the oils it is necessary to use the 
spray pump, i.e. repeatedly fill the chamber with oil in proper propor- 
tions, introducing the nozzle end of the hose, and churn a few minutes. 

How to Apply Oil. — Simply pouring on the oil with a dipper is 
wasteful and requires some little time if all the smaller adjacent 
pools of water are to be treated. Experience has taught that the 
small, apparently insignificant pools of water are in reality the 
greatest menace and are commonly overlooked. The use of a knap- 
sack spray pump (Figs. 96 and 99) of five-gallon capacity is highly 
recommended. This can be strapped on the back and will provide 
enough oil for twenty minutes' continuous spraying or one or two 
hours of ordinary oiling. Where it is out of the question to use a horse 
and cart to carry the oil, the field man can save himself many steps and 
some embarrassment if he will make it a habit to carry a small quantity 




Fig. 97. — The leaking faucet with the re- 
sulting pool of water is often a constant 
menace in the entire absence of other 
mosquito-breeding sources. 



124 



MEDICAL AND VETERINARY ENTOMOLOGY 



of oil with him at all times in a pint or quart tin to which is attached a 
rubber bulb and a spray spout. The inspector usually devotes a day or 




Fig. 98. — Receding streams leave pools of standing water along the banks, in which 
mosquitoes may breed plentifully. 

two to inspection and follows this with an entire day of oiling and he may 
then need to use a good many gallons of oil in a few hours. A good-sized 




Fig. 99. — Showing use of knapsack spray pump in mosquito control. 



MOSQUITO CONTROL 125 

wad of cotton waste soaked in oil and placed in a pool of stagnant water 
will continue to give off oil for some time and is often very serviceable. 

When to Apply Oil. — Oil should be applied whenever and wherever 
the wrigglers. and tumblers are found, even though permanent correction 
is planned. This will prevent them from being washed out into some 
other situation where they would be liable to complete their transforma- 
tion. The frequency with which oil must be applied depends on the 
rate of development of the wrigglers and the evaporation of the oil, — 
both conditions being dependent on the temperature. Therefore, more 
frequent applications are necessary during midsummer, when with the 
oil mentioned above, spraying should be repeated at least every twelve 
days, and under cooler conditions (averaging 50° to 60° F.) every three 
weeks. If it requires only ten days for some mosquitoes to pass through 
their entire transformation, one might think that applications of oil 
every twelve days would not be often enough, but it must be remem- 
bered that the oil kills all wrigglers and tumblers at the time of contact 
and the film remains on the water for about two days, sometimes longer, 
during which time any adult mosquito, intending to lay eggs, is killed 
on coming in contact with the oil. After the oil has evaporated quite 
largely, the breeding may begin again, but the next application of oil 
will catch the oncoming brood before the ten days necessary for com- 
plete development have expired. 

Copper Sulphate. — Treating water with copper sulphate (CuS0 4 ) 
for the destruction of mosquito larvae and pupae has been proved ineffec- 
tive, but it is nevertheless useful in cases where stagnant water is cov- 
ered so badly with algae as to retard the effect of insecticides. The writer 
has invariably had better results with oil applied to algae-covered ponds 
after liberal treatment with copper sulphate, than when the latter was 
not applied. The same also held true for soapy laundry pools which have 
frequently been found to harbor abundant Anopheles larvae. Copper 
sulphate is ordinarily used not in excess of one part per million of water. 

Tobacco Decoctions. — The writer has thoroughly tested the effi- 
ciency of tobacco decoction, both in the laboratory and in the field, and 
has found it very effective, but the expense is prohibitive when it is used 
on a large scale. Sulphate of nicotine (Black leaf 40) made by the 
Kentucky Tobacco Products Company, was found to effectively de- 
stroy all wrigglers and tumblers when used in the ratio of 1 part to 750 
parts of water. Greater dilution proved uncertain for the pupae, but 
1 to 1000 is still effective for larvae. In field work this material was 
effectively used on smaller pools and also on a good-sized quarry-hole 
pond, but the cost proved too great. Ordinary " Black leaf " tobacco 
decoction cannot be used effectively in a greater dilution than 1 part 
to 20 of water. It must be remembered in all cases that a material in 
weaker strengths would be just as useful and less expensive provided 
it killed the insect, even after a day or two, and this factor was borne in 
mind during the progress of experimentation. 



126 MEDICAL AND VETERINARY ENTOMOLOGY 

Smith found that " Nicofume " destroys all small wrigglers at the 
rate of 1 part in 2500 parts of water, and all wrigglers and eventually all 
tumblers at the rate of 1 part to 1500 parts of water. Rapid destruction 
was accomplished by using 1 part of " Nicofume " to 750 parts of water. 

Other Larvaecides. — Many chemicals have been used experimentally 
against mosquito larvae with more or less success, but in most cases 
either the cost or danger to life is forbidding, leaving oil still the sim- 
plest and cheapest remedy. Among the more effective remedies may be 
mentioned " Chloronaptholeum " used as a spray especially in cess- 
pools and other unsanitary situations ; Phinotas oil acts quickly as a 
poison even at very low concentrations, but should not be used where 
there is danger of poisoning. The simple addition of lime or chloride 
of lime to damp places with just enough water present to breed mos- 
quitoes proves quite advantageous. 

The writer's enthusiasm to carry on extensive experimentation with 
larvaecides, except as already noted, has never been fully worked up, 
owing to the fact that such materials are too often taken as an excuse for 
the more satisfactory permanent methods. The general public desires 
above all things a kind of magic remedy to be applied once with little 
trouble and permanent relief, whether the appearance of things has been 
improved or damaged, it matters not. 

The use of larvaecides has, however, a very important place in the 
crusade against the mosquito, and until communities, whether large or 
small, learn to appreciate the advantage attained by proper drainage 
facilities and careful attention to prevent water from becoming stagnant, 
both early and late in the year, these materials must be used. 

At the beginning of a campaign, when larvae and especially pupae are 
already present, a good larvaecide must be applied until proper drainage 
is secured. 

"Larvicide," generally used in the Panama Canal Zone, is prepared 
from crude carbolic acid. Its manufacture and method of application 
are fully described in an article by G. T. Darling in the American Jour- 
nal of Public Health for February, 1912. From this the following is 
quoted : 

" One hundred and fifty gallons of crude carbolic acid are heated in 
an iron tank having a steam coil with steam at 50 pounds pressure. 
Two hundred pounds of finely crushed and sifted common rosin are 
dissolved in the heated acid, and then 30 pounds of caustic soda dissolved 
in six gallons of water are added. There is a mechanical stirring rod 
attached to the tank. The product is ready in a few minutes, yielding 
about 3| barrels. As a mosquito larvicide it is used by spraying an 
aqueous emulsion (one part of larvicide to five of water) over the surface 
and along the margin of pools and ponds or other mosquito-breeding 
places so that the resulting dilution of the larvicide has a thin, milky 
opalescence representing approximately a dilution of 1 to 5000/' Water 
thus treated is poisonous to animals. 



MOSQUITO CONTROL 



127 



Permanent Corrections. — If a useless pond of water can be drained 
readily or filled, and this is very often the case, it is a foolish waste of 




Fig. 100. — Upper figure shows a big pond adjacent to the railroad and caused by ob- 
structing the natural drainage. A source of many mosquitoes every year. Oiling, 
while serving the purpose, requires repeated expenditure of time, labor and money. 
The lower figure shows the same spot after it had been permanently corrected by the 
railroad company. 



time, energy and money to repeatedly oil it. Marshy land, otherwise 
useless for agricultural purposes, can in many instances be made tillable 
and at the same time free from mosquitoes by digging ditches of neces- 
sary depth together with proper lateral branches. Thus many acres 
have been reclaimed, made productive and at the same time inhabit- 



128 MEDICAL AND VETERINARY ENTOMOLOGY 

able. The dry summers prevailing in some sections, notably California, 
favor permanent corrective work, because pools of standing water 
drained off at the termination of the rains in spring remain dry for the 
rest of the summer. The wisdom of permanent corrective measures is 
recognized by all larger business interests as witnessed by their response 
to requests for aid in mosquito control (Fig. 100). 

Irrigation. — It is quite commonly asserted that malaria makes its 
appearance together with irrigation. That is apparently true, but it 




Fig. 101. — Breaks in the irrigation ditch are responsible for considerable inundation, pro- 
ducing favorable breeding places for mosquitoes, especially Anopheles. The rapidly 
running water in the ditch is unfavorable for mosquitoes. 



need not be so if. proper attention were paid to the best methods of 
irrigation. Certainly southern California is necessarily the scene of 
much irrigation, yet malaria is quite scarce, therefore irrigation as such 
cannot be a factor. The matter simply resolves itself to relative abun- 
dance of water ; i.e. where this is abundant, as in northern California, 
it is used unsparingly and without regard for "leaky" ditches (Fig. 
101) and great waste, resulting in ideal swamp areas for the propagation 
of the Anopheles mosquito. 

With proper attention to irrigation methods, particularly drainage 
(Fig. 102), and the use of concrete, tile or metal waterways to prevent 
useless lateral seepage there need be absolutely no malaria associated 



MOSQUITO CONTROL 



129 



therewith. Water should not be permitted to stand in pools for long 
periods, — usually twenty-four hours is sufficient. Water which has 
been standing ten days or over is dangerous, because it only requires 
ten days at the shortest in midsummer for the commoner species of 
mosquitoes to develop from the egg to the adult. Water that runs 
freely in the ditches is not favorable to the propagation of these insects. 




Fig. 102. 



Drainage water resulting from irrigation, a source of myriads of mosquitoes. 
The small ditch in the background will remove the difficulty.. 



The poorly kept ditch is a bad investment in every way, an eyesore and 
a menace to health. 

River Towns and Malaria. — As long as a river is high there will be 
little or no opportunity for mosquitoes to breed along its banks, but 
later in the summer, during June and July, many pools are left behind 
by the receding water (Fig. 98). The stagnant water becomes green 
with alga? and soon Anopheles are breeding in abundance. The same 
condition also commonly prevails along smaller streams. Many mos- 
quito wrigglers may often be found developing in pools covered 
with green scum, and along the edges of the stream or creek where the 
current is very sluggish. In both cases the situation is controllable, 
as has been demonstrated. The pools along the banks of the receding 
river can be drained off, in nearly all cases, or can be thoroughly oiled. 
Thus a river town need not necessarily be a malarial town. And fur- 
thermore, the banks of a river or creek can be kept clean at a compara- 
tively small cost and this need only be done for a distance of about 300 
yards on either side of the community ; in most cases a hundred yards 
less will serve very well because the Anopheles mosquitoes are not strong 
fliers, being bred as a rule very near the place where they are found. 

Salt Marsh Mosquitoes. — Although the Anopheles does not breed 
in salt or brackish water to any great extent, some of the most formidable 
" biters " do, and, moreover, these latter may be carried by the winds 



130 



MEDICAL AND VETERINARY ENTOMOLOGY 



for several miles from their breeding grounds and make life miserable 
for people living in communities unfortunate enough to be in the path 
of the invading horde. This can be corrected, however, for it is found 
that not all portions of a marsh are a menace. For example, the writer 
examined several miles of marsh in a given locality to locate the source 
of the pest and discovered that the breeding ground was restricted to a 











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Fig. 103. — Mosquito control work on a large scale. Permanent corrective work, 
draining a large pond in the background. Salt marsh work in California. 



comparatively protected area comprising only a few acres. For control 
it was recommended that ditches three to four feet deep be dug from the 
open water to the dry land, connecting these main ditches with short 
laterals, in order that the tide waters might sweep clear in and also to 
permit the extremely voracious little killifishes (Fundulus) to find their 
way unobstructed into every nook and cranny of the marsh. 

The most extensive and elaborate salt marsh improvement work has 
been done in New Jersey under the direction of Smith, 1 the permanent 
results of which have more than repaid the amount appropriated for 
the purpose. Land which was previously useless became available for 
agricultural purposes and for summer homes, the increase in real estate 
valuation being an important factor (Fig. 103). 

Summer Resorts. — An ideal summer resort is one in which mos- 
quitoes do not take a prominent part. The Anopheles may not have 

1 Smith, J. B., 1904. Report of the New Jersey State Agricultural Experi- 
ment Station upon the Mosquitoes occurring within the state, their habits, life 
history, etc. 



MOSQUITO CONTROL 131 

to be contended with, but the Culicine species are found more or less 
abundantly everywhere unless measures are taken to control them, and 
some of our summer resorts are far from ideal in this respect. 

Imagine the joy and comfort of a mosquitoless summer resort on a 
fine summer evening under otherwise favorable circumstances, when it 
is possible to sit on the veranda without having to fight mosquitoes all 
the time ! The ease with which these pests can be controlled and the 
advertisement that a mosquito-free resort deservedly secures should set 
managers working in this direction. 

Screening. — Far too little attention has been paid to the proper 
screening of sleeping apartments. The time will come when screens 
will no longer be needed against intruding mosquitoes and flies, — 
indeed that day has already dawned for a few (a very few) thoroughly 
enlightened communities, which have discovered that these noxious 
creatures can be readily controlled. 

Against mosquitoes nothing larger than the best one-millimeter 
mesh (No. 18) screen should be used. Mosquitoes are persistent and 
will work their way through a large mesh. Furthermore, in malaria- 
ridden districts it is time well spent to hunt down and destroy all mos- 
quitoes that may have secured entrance despite the screens. It is also 
wise to carefully screen in all malaria cases at night so that Anopheles 
mosquitoes cannot become infected through the blood of such patients. 

Campers, prospectors, soldiers, and others required to sleep out of doors 
should use special folding frames covered with mosquito netting. These 
are light and can be folded to convenient size for portage when not in use. 

Cisterns, fire buckets, and other water receptacles need to be kept 
properly screened or securely covered. 

Repellents. — Night laborers, watchmen, pickets, and others com- 
pelled to be on duty at night are, of course, exposed to the bites of mos- 
quitoes and should exercise some precaution at least against these 
pests. Repellents of several kinds have been used with more or less suc- 
cess. The writer has found oil of citronella to be one of the most reliable 
deterrents when simply rubbed on the hands and face ; a dozen drops or 
thereabouts being placed in the hollow of the hand and thus applied. 

To this oil may be added various other ingredients; for example, 
Howard has found the following mixture most effective, viz. : 1 ounce 
of citronella, 1 ounce spirits of camphor, and one half ounce oil of cedar. 
Howard found this very satisfactory against Culex pipiens by applying 
a few drops on a bath towel hung on the head of the bed. He, however, 
adds that it is not effective against the yellow fever mosquito, which 
begins biting at daybreak when the oil has lost most of its strength. 

Other deterrents used and recommended by various authors are : a mix- 
ture of castor oil, alcohol, and oil of lavender, equal parts ; or a few drops 
of peppermint or pennyroyal, oil of tar, oil of cassia, or simply pure kerosene. 

Repellent Plants. — Much has been written about deterrent trees 
and plants, but few, if any, have stood the test of accurate observation. 



132 MEDICAL AND VETERINARY ENTOMOLOGY 

The writer's own experience together with that of other observers, does 
not credit the castor-oil plant nor the Eucalyptus tree with important 
deterrent properties; the same seems to hold true of the chinaberry 
tree and the pennyroyal plant. 

Fumigants. — Knowing that mosquitoes often hibernate in great 
swarms in basements of buildings, cellars, and other favorable situations, 
it becomes necessary to destroy these in order to prevent them from 
propagating in the spring of the year. A number of very satisfactory 
fumigating agents may be mentioned, such as pyrethrum powder, sul- 
phur dioxid (see p. 75), fumes of cresyl, -pyrofume (a turpentine by- 
product), etc. J. B. Smith recommends Jimson weed fumes very highly. 
He recommends using powdered Jimson weed {Datura stramonium) 
at the rate of eight ounces per 1000 cubic feet of space, mixing it with 
one-third its weight of saltpeter to facilitate combustion. The mixture 
is to be spread on a tin pan or stone and ignited at several points. The 
fumes are not dangerous to human life. 

Mosquito Bites. — Mosquito bites, while perhaps never serious in 
themselves, may lead to blood poisoning through scratching with the 
finger nails in the attempt to relieve the irritation, often intense. To 
relieve this irritation any one of the following may be applied, viz. : 
ammonia, glycerine, alcohol or iodin. According to Howard the most 
satisfactory remedy known to him is the application of moist toilet soap. 
He also mentions touching the puncture with a lump of indigo as afford- 
ing instant relief, or touching the parts with naphthaline moth balls. 

Natural Enemies. — One often hears others say that there is a natural 
" balance " in nature which should not be disturbed, and this argument 
is frequently advanced against the efforts of those engaged in mosquito 
control. It may be balm to such individuals to know that mosquitoes 
have also their natural enemies, if man can indeed be considered an 
unnatural enemy. 

Among the less efficient enemies, owing to small numbers, are the 
dragon flies (Odonata), commonly called " mosquito hawks," " snake 
doctors," and "devil's darning needles." These insects may be seen in 
the evening darting hither and thither capturing mosquitoes and midges 
on the wing. Where bats are plentiful, these animals are highly spoken 
of as effective enemies of mosquitoes. 

More effective enemies are found among the surface-feeding fishes, 
which are practically all of small size. Unfortunately, where mosquito 
larvae are found there are also abundant other aquatic insects, so that 
the stock of fish must be correspondingly large in order to hold in check 
the insects aimed at. In such places where it is undesirable to apply 
oil and the water is not too shallow throughout its entire extent, fishes 
may play an important role; indeed the same thing may hold true 
in bodies of water where it is quite possible to apply oil. It can readily 
be seen that to transplant fish into anything but permanent bodies of 
water would be very poor policy. Ornamental ponds, reservoirs, 



MOSQUITO CONTROL 133 

springs, cisterns, tanks, and the like are among the instances in which 
surface-feeding minnows may be found useful. 

The common goldfish (Carassius auratus) is at the same time one of 
the most ornamental as well as efficient fishes in this respect. The 
following quotation from Howard * after Underwood, referring to an 
ornamental aquatic garden near Boston, in which mosquitoes were 
kept in check by goldfish is apropos : "I took from the pond a small 
goldfish about three inches long and placed it in an aquarium where it 
could if it would, feed upon mosquito larvae and still be under careful 
observation. ... In the first day, owing perhaps to being rather easily 
disturbed in its new quarters, this goldfish ate eleven larvae only in three 
hours, but the next day twenty-three were devoured in one hour ; and 
as the fish became more at home the ' wigglers ' disappeared in short 
order whenever they were dropped into the water. On one occasion 
twenty were eaten in one minute, and forty-eight within five minutes. 
This experiment was frequently repeated and to see if this partiality for 
insect food was characteristic of those goldfish only which were indige- 
nous to this locality experimented with, some said to have been reared 
in carp ponds near Baltimore, Maryland, were secured. The result 
was the same. ..." Similar results have been attained in a number 
of places both on the Atlantic and Pacific coasts. 

One of the most valuable articles touching the control of mosquitoes 
by fish is that of Seal 2 for the Scientific American, in which he makes 
the following statements : " The goldfish is somewhat lethargic in 
habit, and is also omnivorous, but there is no doubt that it will devour 
any mosquito larvae that may come in its way or that may attract its 
attention. The one great objection is that they grow too large, and the 
larger will eat the smaller of them." The same observer concludes that 
" a combination of the goldfish, roach, and top minnows would prob- 
ably prove to be more generally effective in preventing mosquito breed- 
ing than any other." The top minnows mentioned are Gambusia affinis 
and Heterandria formosa. In those bodies of water kept free from mos- 
quito larvae in California, McGregor, working for the writer, has observed 
that the following three species are primarily concerned, viz. : the Sacra- 
mento chub, Leuciocus crassicandra, the Sacramento pike, Ptychocheilus 
grandis; and the shiner, Lavinia exilicauda. The Barbadoes " mil- 
lions " (Cyprinodon dispar) has been found useful as a mosquito de- 
stroyer in that country and elsewhere. In salt marshes the tiny killi- 
fishes (Fundulus) should be given every opportunity to reach all parts 
of the marsh. Where found, they are, as a rule, very abundant and are 
efficient as destroyers of mosquito larvae. 

Organization. — In order to conduct an effective civic anti-malaria 
mosquito crusade, there must be some responsible organization back of 
it. This may be a new body or an organization already in existence. It 

1 Howard, L. O., 1910 (loc. cit). 

2 Seal, William P., 1908. Scien. Amer. Suppl., Vol. 65, No. 1691, pp. 351-352. 



134 MEDICAL AND VETERINARY ENTOMOLOGY 

is absolutely essential that a committee at least be responsible as a 
medium between the citizens and the persons doing the actual control 
work. 

In the several anti-mosquito crusades under the writer's direction 
the financial responsibility was undertaken in one case by a new organ- 
ization under the name of " The . . . Anti-Mosquito League," with a 
president, vice president and secretary treasurer ; in another case it 
was a committee of representative citizens with a chairman, a secretary 
and a treasurer ; the committee was known as " The . . . Anti-Malaria- 
Mosquito Committee " ; and in still another crusade the responsibility 
was undertaken by the " Mosquito Committee " of the Woman's Club. 
In no case could it be said that the mosquitoes were worse than in 
neighboring towns which might have led to such action, but the initia- 
tive could be traced to the progressive spirit of one or more citizens. 

The financial responsibility having been undertaken by the respec- 
tive organization, and a previous estimate of cost having been provided 
by some one familiar with such work, the next step in the campaign is 
to secure the services of a trained field agent or sanitary inspector who 
is to do the actual control work assisted by day laborers. 

The Inspector or Field Agent must be an individual not only quali- 
fied technically but must have the ability and patience to inform those 
with whom he comes in contact as to the reason for his action if the work 
is to be of lasting benefit. This does not imply, of course, that words 
should be lost on persons who purposely interfere on the ground of igno- 
rance, — he must therefore also be firm. Since sanitary inspectors in 
many communities are grossly incompetent, and are merely so-called 
inspectors, whose duty it is to occasionally peer into a toilet or tack up 
a contagious disease placard, the office does not imply the dignity that 
it ought, therefore the term field agent, was preferably employed in the 
writer's work in California. 

With a responsible field agent in charge whose sole duty it is to 
protect the health of the community through the control of mosquitoes 
the success of a crusade should be assured. 

The Cost. — The cost of an effective campaign is thought by some 
to be quite forbidding, but experience under conditions often apparently 
hopeless has shown that everything necessary can be done within rea- 
sonable limits. One good field agent can handle from eight to ten 
square miles of territory, and the salary of this individual represents 
the greatest outlay, unless much permanent corrective work is done, a 
matter which would increase the cost in the beginning, but would pay 
in the long run. The actual field work need not extend over much more 
than eight or nine months, from March to November inclusive at most. 
Capable men can usually be secured at a salary ranging from S75 
to S125 per month, new men beginning with the first mentioned sum. 

Considering the benefits derived in added comfort and improved 
health, double the cost above mentioned would be reasonable. It should 



MOSQUITO CONTROL 



135 



be noted that in every crusade of this kind the general health conditions 
are improved. 

In order that a campaign may be successful and that the work may 
continue unhampered, it is essential that sufficient funds be in sight to 
begin with. Raising funds is a matter that must be settled by each 
community for the present until such legislation has been brought about 
that will insure county or state aid. Thus far the task of raising funds 
has ordinarily been given over to the civic organizations which have 
solved the problem in one way or another through committees. Sev- 
eral committees have raised their funds by popular subscription; one 
other progressive town has had several tag days with gratifying results. 

Under California conditions, for example, the average minimum cost 
of protection, giving to each field agent an area of ten square miles 
to cover, which is possible with some assistance, is about $.75 per day 
per square mile. At this rate the cost of an average crusade covering 
an area of ten square miles is about SI 600 for one season, covering a 
period of eight months. Estimating the cost of quinine and doctors' 
bills at $20 per family, with not more than one hundred families within 
the ten square miles area (a low estimate) plus 25 per cent reduction in 
earning capacity per family with an average income of S800, gives a 
total loss of $20 X 100 (= S2000) + S800 X 100 X 25 per cent 
(= $20,000) = $22,000. Ordinarily it is possible to reduce the total 
amount of malaria by at least 50 per cent in one season. At this rate 
there is a saving of $22,000 X 50 per cent - $1600 = $9400 (nine 
thousand four hundred dollars) in one season to this scattered rural 
community. Surely this is a good investment. 

The following table (Table II) is intended to give an idea of items 
involved in the monthly expense account. 

TABLE II 

Tabular Account of Monthly Expenses (for Oroville) 1 from March to 

July Inclusive, 1911 





March and April 


May June 


July 


on 

Rig hire ...... 

Printing and stationery . 

Postage 

Labor 2 

Sulphur 

Field Agent 


$15.10 

9.50 

11.50 

1.60 

[March 10.00 
(April 125.00 


$2.50 
10.50 

.50 
125.00 


$16.90 
9.00 

2.00 
.50 

125.00 


$25.45 
9.00 

.50 
125.00 




$182.70 


$138.50 


$153.40 


$159.95 



1 The greater part of this work was confined to an area of about four square 
miles, including the city of Oroville, California, and only about one fifth of the 
time was spent in inspecting the rural surroundings. 

2 Practically all labor, to the value of approximately $120, paid by city 
street department and several private companies. 



136 



MEDICAL AND VETERINARY ENTOMOLOGY 



The above estimate of $.75 a day per square mile of protection does 
not include much permanent corrective work, and would continue from 
year to year without lessening greatly, though the educational factor 
will play an important part after two or three years, when individuals 
in a community will do considerable work of their own accord. 

The following estimate (Table III), based on a thirty square mile 
area and including all necessary permanent corrective work of ordinary 
nature, shows conclusively that a larger primary investment is the 
cheapest in the end and certainly far more satisfactory. 

TABLE III 

Estimated Cost of Malaria Control Covering a Thirty Square 
Mile Tract and Including all Ordinary Permanent Corrections. 
Based on a Taxation Plan. 



Items 



Assessor 

Director 

Field Agents 

Surveys 

Maps 

Stenographer .... 
Equipment (Teams, etc.) 

Labor 

Materials 

Feed .' 

Supplies 

Office (postage, etc.) . . 

Oil . 

Incidentals 

Ten per cent contingencies 



Approximate cost 
mile per day . 



per square 



First Year 



$1000 

2500 

3200 (3) 

2500 

750 

900 

2000 

3000 

1500 

700 

100 

100 

350 

200 

18800 

1880 



Square miles 30 )20680 
Days 365)689 



$1.90 



Second 
Year 



$500 

2000 

2400 (2) 



200 

200 

250 
50 

100 

200 

100 

6000 

600 

30 )6600 

365)220 



.60 



Third 
Year 



$200 

400 
1500 (1) 



100 

120 

100 
100 
100 

2620 
262 



3 0)2882 
365)96 



$.27 



When to Begin Work and when to Close. — The best results are 
secured in a new district by eliminating as far as possible the last brood 
of mosquitoes in the autumn, i.e. oil or drain off all mosquito breeding 
pools in October and go over the territory once again in November. 
In this way the number of mosquitoes which hibernate over winter is 
reduced to a minimum. The spring work should begin in March, 
depending on the weather, — if warm, the work must begin earlier in 
the month, if cool, then later. This can only be ascertained by inspect- 
ing likely pools in order to determine whether mosquito larvae are pres- 



MOSQUITO CONTROL . 137 

ent and what size they have attained. Usually the last larvae are found 
in October and the campaign may usually close safely with the end of 
this month. This applies to the Anopheles mosquito (the malaria 
bearers) and does not apply to the Culicine varieties, including salt 
marsh species. 

The Educational Factor. — Giving the answer to the questions, 
" Why? " and " How? " is the part the educator must play in the 
science of sanitation. If once the people of a town Or village catch the 
vision of better things, and are taught how to realize these things, the 
problem is largely solved. 

To help answer these questions at least one lecture, well illustrated 
by means of charts, lantern slides, and other material, should be given 
at the beginning of each campaign. This we generally follow up with 
brief newspaper articles, for the press is one of the greatest educational 
factors in America. Show window displays, in which the properly labeled 
living insects are exhibited as they pass through their various stages of 
development. Also the action of the oil can be thus nicely illustrated. 
The interest that this sort of display arouses is immense and few mer- 
chants hesitate to allow at least a part of their windows to be so used. 

A laboratory may or may not be established in which the more 
scientific phases of the subject are illustrated by means of the microscope 
and other apparatus. The writer has found such laboratories very 
valuable since it gives the field agent an added impetus and adds to his 
efficiency in the field. Here the more detailed habits of the individual 
insect can be observed. 

One of the most important factors in our work is that accomplished 
through the school children. The school children are visited in the 
classroom and the story of the mosquito wriggler is told, — how the 
mosquito carries disease and how to prevent it. Demonstrations with 
the living wrigglers can easily be made. Interesting essays are then 
written by the children and the best may be published in the local paper, 
all of which stimulates interest and gives the children a grasp on prac- 
tical subjects. The lessons (Fig. 104) learned at this time will be ap- 
plied at once, and a generation of citizens is reared with some knowledge 
of practical hygiene. 

The use of a mosquito pin or button has resulted in much good. On 
answering some simple question, or after putting oil on a pool of water, 
the child receives such a pin from the inspector as a reward of merit. 

Legislation. — In any malaria crusade all the inhabitants of a given 
district are equally benefited ; it is therefore unreasonable that the en- 
tire cost of a campaign should be borne by a few individuals, which has 
been the case in several localities where funds were contributed through 
popular subscription. Because of the equal benefits derived, some plan 
of assessment or state appropriation seems to be more reasonable ; how- 
ever, the latter (state appropriation) may be objectionable unless all 
parts of the state are concerned. It should be borne in mind after all 



138 



MEDICAL AND VETERINARY ENTOMOLOGY 



that bad advertising for one part of the state means injury to every 
other part, and the fact that malaria is present in any state is bad 
advertising. Be it also known that no community can hide the fact 
that malaria is present within its bounds, however strenuously its pres- 
ence is denied. To carry on an anti-malaria campaign and then to 
widely advertise the fact is the best sort of advertising. Note the 
change of heart suffered by real estate dealers and boosters in several 
of the more progressive towns in malaria-ridden districts. 




Fig. 104. — School children taking lessons in practical hygiene. The little boy in the 
foreground is preaching the gospel of good health to hundreds of children in many 
parts of the land by this example. 



In January, 1911, an act known as the Guill Bill was introduced in 
the California legislature, and was passed by both houses, but did not 
receive the governor's signature. Had this bill become a law, it would 
have been the first state enactment of its kind in the United States 
directed specifically towards the extermination of the Anopheles mos- 
quito by local communities with the object of controlling malaria. 

The bill provided that the Board of Supervisors in any county, on its 
own motion or upon receiving a petition from ten or more taxpayers in 
the proposed district, should pass a resolution declaring its intention to 
do all work necessary for the extermination of Anopheles mosquitoes, 
describing the boundaries of the district to be benefited and assessed 
for the benefits. The petition mentioned was required to give the bound- 
aries of the proposed district, to show that a survey had been made 
of the district under the direction of the State Board of Health, and 



MOSQUITO CONTROL 139 

that such survey showed that there were one or more breeding places 
of Anopheles mosquitoes within the proposed district. 

The resolution of intention to do the work was required to be pub- 
lished, and opportunity was given to any one who objected to the work 
to appear before the Board and state his reasons for objecting. If 
they were not valid, the Board was to proceed to order the work done, 
appointing three commissioners to assess benefits and damages and have 
general supervision of the work. These commissioners were to have 
made a thorough sanitary survey of the district, make and map a 
careful description of the work required, and report the same to the 
Board of Supervisors. All objections to this report or any portion 
of it were then to be filed in writing with the county clerk, and at the 
next regular meeting of the Board these objections were to be heard and 
sustained or rejected or modified according to the judgment of the Board. 

Certified copies of the report, assessment roll, and map were then to 
be filed with the tax collector, the taxes were then to be payable, and 
work to proceed as funds became available. 

The state of New Jersey enacted effective legislation against salt 
marsh mosquitoes in 1906 ; the act reads : " An act to provide for 
locating and abolishing mosquito-breeding salt marsh areas within the 
state, assistance in dealing with certain inland breeding places, and 
appropriating money to carry its provisions into effect " and " for the 
purpose of carrying into effect the provisions of this act, the said Direc- 
tor of the State Agricultural Experiment Station shall have power to 
spend such amount as may be appropriated by the legislature, provided 
that the aggregate sum appropriated for the purpose of this act shall 
not exceed three hundred and fifty thousand dollars. " 

The first sound county legislation in the state of California has been 
enacted by the county of Tehama and reads as follows : 

" Ordinance No. 46 

" An ordinance to exterminate the mosquito larva. 

"The Board of Supervisors of the County of Tehama, State of California, 
do ordain as follows : 

" Section 1. No person or persons, firm or corporation shall discharge, 
pour, empty out, or otherwise place upon the surface of the ground in any lot, 
yard, street, road, alley or premises within the limits of the County of Tehama, 
State of California any water from any source which remains in a stagnant 
condition within two thousand (2000) feet of any occupied dwelling house, or 
maintain water in stagnant condition in any barrel, can, tub or open re- 
ceptacle of any character whatsoever, within two thousand (2000) feet of any 
occupied dwelling house. The presence of the mosquito larva in said water shall 
be conclusive evidence that said water is stagnant, and upon the finding of said 
mosquito larva the occupant, or if the premises are unoccupied, the owner, 
shall be liable to arrest, fine and imprisonment as hereinafter provided, and if 
the said stagnant water, which is hereby deemed a nuisance, be not drained 
away or treated in a manner satisfactory to the Health Officer of Tehama 
County or his authorized representative, and within a reasonable period of 



140 MEDICAL AND VETERINARY ENTOMOLOGY 

time as determined by the Health Officer or his authorized representative, the 
said nuisance shall be abated by the Health Officer. The cost thereof shall be 
paid from the General Fund of the Treasury of Tehama County upon sworn 
warrant of the Health Officer, and the cost of said abatement shall be a lien 
upon the property upon which the said nuisance was created and abated, and 
shall be collected by law as taxes are collected. 

" Section 2. Wells, cisterns, cesspools and privy vaults shall be so screened 
or covered as to prevent access to the contents thereof by mosquitoes, and 
such screens or covering shall be maintained in good condition and to the satis- 
faction of the Health Officer of Tehama County. 

11 Section 3. All violations of this ordinance shall be a misdemeanor, pun- 
ishable by a fine of not less than five ($5.00) dollars nor more than fifty 
($50.00) dollars, or by imprisonment in the County Jail for not less than five 
(5) days or more than fifty (50) days, or by both such fine and imprisonment." 

Malaria Reduction as the Result of Anti-mosquito Measures is 

nicely shown by the following table (Table IV) after Cassa : 1 



TABLE IV 
Showing Deaths from Malaria in Havana from 1872 to 1911 Inclusive 

The enormous reduction in deaths will be seen to begin with the inauguration 
of anti-mosquito measures in 1901. 



Years 


Total Deaths 


Death Rate 


Years 


Total Deaths 


Death Rate 


1871 


262 


1.33 


1892 


286 


1.33 


1872 


316 


1.60 


1893 


246 


1.12 


1873 


329 


1.61 


1894 


201 


0.90 


1874 


288 


1.45 


1895 


206 


0.90 


1875 


284 


1.43 


1896 


450 


1.95 


1876 


334 


1.68 


1897 


811 


3.48 


1877 


422 


2.12 


1898 


1907 


8.00 


1878 


453 


2.28 


1899 


909 


3.76 


1879 


343 


1.72 


1900 


325 


1.30 


1880 


384 


1.93 


1901 


151 


0.55 


1881 


251 


1.26 


1902 


77 


0.29 


1882 


223 


1.12 


1903 


51 


0.19 


1883 


183 


0.91 


1904 


44 


0.16 


1884 


196 


0.98 


1905 


32 


0.11 


1885 


101 


0.50 


1906 


26 


0.08 


1886 


135 


0.67 


1907 


23 


0.08 


1887 


269 


1.34 


1908 


19 


0.06 


1888 


208 


0.99 


1909 


6 


0.01 


1889 


228 


1.11 


1910 


15 


0.05 


1890 


256 


1.23 


1911 


12 


0.03 


1891 


292 


1.37 















Figures 105 and 106 show T graphically the results of anti-mosquito 
work at Ismailia and at Panama. 



1 Cassa, Jorge Le Roy Y., 1913. Sanitary Improvement in Cuba as demon- 
strated by statistical data. Amer. Journ. of Public Health, No. 3, Vol. III. 



MOSQUITO CONTROL 



141 



Results Obtained in Combating Yellow Fever Mosquitoes. — The 
table on next page, taken from Doane, 1 shows the death rate in Havana 



■ Ee*> \ - I -4 .. ._ I\ j \/fw 
\ '■ I \ 1 \ 

* LiJl ijTi.n 


— '- — p w. 

SSAfAfl/A 

tKtat&Q? e/'o?jrj &zc4 year. _: , . 

/ram .raSsfcofeE ar'jt&tasetf'jftk 
/f/~Grsry_ 

\| 111 | '|~| ' 


| 
] 

f ' 
1 
; 

! 


r _ r 









Fig. 105. — Curve showing reduction of malaria at Ismailia (Suez Canal) with the appli- 
cation of anti-mosquito measures in 1902. 

due to yellow fever from the years 1893 to 1902 inclusive; the work of the 
Yellow Fever Commission based on mosquito control having been put 



/*/a/a/~/a <5/a//s//es a/ 
/^ZIA/AMA 

j/>o*w/y /Ae *vm£er of drafts 
per year *4rtye rew/rt/e/zo/r 
tomme/rced <n /896 
foorouffi j&rtfaf/en 4epu/> *> 
/9W »»4e/ Co*>ne/ Gorpas 
jM/f-nrnfurfo mvst/rrj 
6<yvn //> /eAruay,/90/. 




ry/,<S>try j 



is | | s | s i | ||. 



Fig. 106. — Curve showing reduction of malaria at Panama (Panama Canal Zone) with 
the application of anti-mosquito measures in 1901. 

into effect in 1901 and 1902. Surely this table is eloquent in its praise 
of this splendid work. 



1 Doane, R. W., 1910. Insects and Disease. Henry Holt & Co., New 
York. pp. xiv + 227. 



142 



MEDICAL AND VETERINARY ENTOMOLOGY 



TABLE V 

Deaths est Havana from Yellow Fever during Years 1893 to 1902 

Inclusive 





1893 


1894 


1895 


1896 


1897 


1898 


1899 


1900 


1901 


1902 


Januarv . . 


15 


7 


15 


10 


69 


7 


1 


8 


7 





February 


6 


4 


4 


7 


24 


1 





9 


5 





March . . 


4 


2 


2 


3 


30 


2 


1 


4 


1 





April . . . 


8 


4 


6 


14 


71 


1 


2 











Majr . . . 


23 


16 


10 


27 


88 


4 





2 








June . . . 


69 


31 


16 


46 


174 


3 


1 


8 








Julv . . . 


118 


77 


88 


116 


168 


16 


2 


30 


1 





August . . 


100 


73 


120 


262 


102 


16 


13 


49 


2 





September . 


68 


76 


135 


166 


56 


34 


18 


52 


2 





October . . 


46 


40 


102 


240 


42 


26 


25 


74 








November . 


28 


23 


35 


244 


26 


13 


18 


54 








December . 


11 


29 


20 


147 


8 


13 


22 


20 












CHAPTER XII 



BUFFALO GNATS AND HORSEFLIES 



A. Buffalo Gnats 



Order Diptera, Suborder Nematocera, Family Simuliidce 

Characteristics. — To the family Simuliidae belong the tiny blood- 
sucking flies commonly called buffalo gnats, black flies, sand flies and 
turkey gnats. They are small dipterous insects ranging from 1 to 4 mm. 
in length, with a curiously humped thorax (Fig. 107) and blade-like pierc- 
ing mouth parts. The antennae are short cylindrical structures consist- 
ing of eleven segments. The 
wings are relatively broad and 
iridescent, and the venation is 
characterized by the strong de- 
velopment of the costal veins, 
the remaining ones being very 
weakly developed or absent. 
The Simuliidae are world-wide 
in their distribution. 

Larvae. — The brown to 
whitish larvae are cylindrical, 
twelve-segmented, slightly 

thinner in the mid region, and 
when fully grown are from 10 
to 15 mm. in length (Fig. 108a). 
The posterior end of the body 
is provided with a toothed disk- 
like sucker, composed of two 
modified parapodia. The an- 
terior proleg is also modified 




Fig. 107 



A buffalo gnat, Simulium sjj. X 18. 



into a prehensile toothed disk. 
By means of this organ, the larva moves from place to place with a 
looping motion. Through the agency of a secretion from the salivary 
glands, the larvae are able to spin a silken thread to which they 
attach themselves, hanging from the end of the thread or moving 
along its length, the thread being attached to rocks or other debris. 
Although the larvae are provided with a well-developed tracheal 

143 



144 



MEDICAL AND VETERINARY ENTOMOLOGY 



system, there are no open spiracles, and respiration is carried on by 
means of gills, recognized as branched retractile structures located 
dorsally on the last abdominal segment. The fan-shaped filamentous 
structures located on the head are for the purpose of creating a current 
by means of which food is drawn to the mouth. 

Pupae. — The pupae are quiescent and are loosely encased in silken 
cocoons or pockets. They are provided anteriorly with a number of 
long tracheal filaments (Fig. 1086), which are also of importance in 
classification. 

Breeding Habits and Life History. — The adult buffalo gnats often 
occur in great swarms during the late spring and early summer in the 

neighborhood of marshes and forest 
streams. Occasionally swarms of these 
insects are seen far removed from 
moisture, but the reason for this is 
usually traceable to prevailing winds. 
At this time of the year the tiny white 
or whitish eggs are deposited in great 
numbers on the exposed, preferably 
wet, surfaces of rocks, grass, moss, 
brush and other debris in shallow 
streams of rather swiftly running water 
by preference. Comstock says he has 
often watched the gnats hovering over 
the brink of a fall where there was a 
thin sheet of swiftly flowing water, and 
has seen them dart into the water and 
out again. At such times he has al- 
ways found the surface of the rock 
more or less thickly coated with eggs, 
and has no doubt that an egg is fastened 
to the rock each time a fly darts into 
the water. 

The time required for hatching is from ten to thirty days, depending 
on temperature. The newly emerged larvae attach themselves to sub- 
merged objects, such as stones, logs, etc., by means of silken threads. 
Movement from place to place is gained by shifting their anchorage. In 
some favorable location, such as the riffles on the downstream side of an 
old log partially damming a little stream, there may be thousands of 
these tiny spindled larvae. The larvae as well as the pupae being 
provided with gill filaments remain submerged. Growth is slow, the 
larval period covering the time from early summer to the following 
early spring, when full larval growth is reached. The larval period of 
some species is said to require but four to five weeks. The food of 
the larvae consists of small Crustacea, protozoa and algae. 

The pupal period is quite short in some species, requiring not over 





Fig. 108. — (a) Larva and (b) pupa 
of Simulium ; latter removed from 
cone-shaped cocoon. (Redrawn after 
Lugger from Washburn.) 



BUFFALO GNATS AND HORSEFLIES 145 

five or six days, while still others evidently require nearly a month. It 
is also true that temperature influences this stage, i.e. cooler weather 
retards the emergence of adults. 

The Bite. — There is perhaps no other insect of equal size that can 
inflict so painful a bite as can the buffalo gnat. The mouth parts are of 
the Dipteron type, consisting of six blade-like lancets. 

Human beings as well as domesticated animals are viciously attacked. 
The eyes, ears, nostrils, wrists and all exposed parts of the body are 
subject to attack. The extreme pain and the resultant local swelling, 
and occasionally complications, indicate the introduction of an active 
venom. 

Losses due to the bite of this fly are estimated variously by stock- 
men. Washburn * states that " in 1884, in Franklin's Parish, Louisiana, 
they killed 300 head of stock in a week. In 1874 the state of Tennessee 
alone lost as much as $500,000 worth of stock from the attack of these 
flies." 

Relation to Disease. — Owing to the intermittent blood-sucking 
habits of the buffalo gnats, it has long been suspected that these in- 
sects might play a part in the transmission of disease, but as a matter 
of fact, little experimental evidence is at hand to verify this suspicion. 
Since anthrax is comparatively easily transmitted from animal to ani- 
mal, inasmuch as Bacillus anthracis is both exceedingly virulent and long- 
lived, it may be supposed that this disease could be transmitted, if any, 
but even here experimental evidence is wanting. 

Since the rather startling statement of Dr. Louis W. Sambon 2 in 
1910, referring the transmission of pellagra to a buffalo gnat, the study 
of Simuliidse with regard to disease transmission has taken new impetus. 

Pellagra. — This disease, also known as Alpine scurvy, sun disease 
and Asturian leprosy, has a very wide geographical distribution in semi- 
tropical countries, especially southern Europe. In the southern United 
States the disease has been increasing an hundred fold during the past 
two years or more. 

The disease is manifested by annually recurring attacks of nervous 
and cutaneous symptoms. The symptoms reappear each year in the 
spring, gradually disappearing during the winter. The nervous symp- 
toms are mainly in the form of melancholia, while the cutaneous symp- 
toms are in the form of eruptions influenced by sunlight. 

Both sexes are alike susceptible as well as all ages, except rarely 
infants. That the disease is most widespread among field laborers and 
country folk living near streams of water, and that the symptoms recur 
with the spring months has led to an investigation of the insect carrier 
theory. Heretofore the maize theory of spread was most generally 

1 Washburn, F. L., 1905. Diptera of Minnesota. University of Minne- 
sota Agr. Exp. Sta. Bull. No. 93. 

2 Sambon, L. W., 1910. Progress Report Investigation of Pellagra. Journ. 
of Tropical Medicine and Hygiene, Vol. XIII, No. 19. 



146 MEDICAL AND VETERINARY ENTOMOLOGY 

accepted, i.e. the theory that the disease was contracted by eating 
infected corn (maize). 

Dr. Louis W. Sambon {loc. cit.) of the London School of Tropical 
Medicine studied the pellagra situation in Italy and in 1910 published a 
note on his investigations, viz. : " So far I have been able to establish : 

" (1) That pellagra is not due to the eating of maize, either sound or 
deteriorated, as hitherto almost universally believed. 

" (2) That it has a striking, peculiar and well defined topographical 
distribution. 

" (3) That its endemic foci or 'stations' have remained exactly the 
same in many places for at least a century. 

" (4) That its stations are closely associated with streams of running 
water. 

" (5) That a minute blood-sucking fly of the genus Simulium is in 
all probability the agent by which pellagra is conveyed." 

Professor H. Garmen of the Kentucky Agricultural Experiment 
Station has carried on recent extensive studies with regard to pellagra, 
and his findings are reported in Bulletin 159 (1912) from which the fol- 
lowing extracts are taken, viz. : 

"Looking at the matter from the point of view of the entomologist and 
naturalist it seemed to me very evident when I had examined only a few cases 
of pellagra that some agent in the air had to do with its spread, and it may be 
of interest to recall the facts that most appealed to me. In the first place the 
eruption on the hands began apparently about the bases of the fingers and ex- 
tended thence upward to the elbows, where it stopped abruptly. On the legs 
it seemed to begin at the feet, affecting the upper surface and extending to the 
knees, where it terminated in a well-marked line. On the head and neck 1 ; it 
affected in all cases examined only the skin constantly exposed, and terminated 
at the han and at the collar. Yet in some instances there is an extension of the 
affected skin down upon the chest, coinciding somewhat closely with the open- 
ing in the shirt front. One such case, which I did not have a chance to see, was 
reported to me as residing at Old Straight Creek, above Pineville. All of these 
conditions seemed consistent with Dr. Sambon's theory that an insect carries 
the virus of the disease from ill to well, attacking the exposed skin and injecting 
into it something, bacteria or protozoa, which gives rise to the disease. 

" Furthermore the disease is contracted and afterward becomes active in early 
spring just the time when our gnats of the genus Simulium come from the water 
in greatest numbers as adults. 

" Again it often affects children, who constantly go barefooted and bare- 
legged in this region and are disposed to play and wade in the streams. "Women, 
too, were affected more than men, about the arms and neck generally, but also 
in some cases on the feet and calves. Men go less frequently with limbs bare, 
and are much less often attacked. The skin trouble appears upon the trunk 
rather rarely, though cases are on record of parts generally kept covered by 
clothing becoming affected. 

"With these facts in mind, it was with very great interest that I examined a 
case at Moss' Camp above Pineville which seemed to oppose the idea of insect 
agency in the disease. The case was that of a middle-aged woman whose arms 
showed in a marked manner the symmetrical development of the skin lesions, 
so often mentioned by writers on the ailment. It was interesting further because 
it was then (Sept. 1) in an active condition, whereas all the other cases examined 



BUFFALO GNATS AND HORSEFLIES 147 

showed the usual summer cessation of the disease and an improvement in general 
health. The affected regions on the two arms were surrounded by a deep red 
border, as if something had got access to the blood in the center of the area and 
was spreading outward into the healthy skin, much as one sees in plants a fungus 
pushing outward from a point of inoculation by a growth of its mycelium. The 
area on the two arms and forearms seemed to be of about equal extent. This 
affected region was such as might at some time have been exposed to the air 
when the patient was busy about her domestic affairs. A more interesting and 
puzzling feature of this case was the presence of two isolated round spots of 
diseased skin, one on the point of each shoulder. If there had been one, I should 
have thought a hole in a gown might at some time have exposed the part to 
infection, but the chances seem against the presence of two such holes exactly 
alike, one on each shoulder. I am giving this fact as an illustration of what 
some physicians claim to be an invariable feature of the ailment, no matter 
where the skin trouble appears, namely, a symmetry in the skin affection, which 
they regard as evidence that the seat of the disease is within and the skin lesions 
only incidental and dependent. The case appears to support this view, jet it 
may prove when we know more of the conditions attending the contraction of 
the disease that such cases are still explainable on the theory of insect agency." 
Pellagra has been carefully studied by the United States Public Health 
Service, and in the Public Health Reports of October 23, 1914, Goldberger 
states that Pellagra is neither infectious nor contagious, that it is essentially 
of dietary origin, dependent on some yet undetermined fault in diet, and that 
the disease does not develop in those who consume a mixed, well-balanced and 
varied diet. 

Gnat Control. — Knowing the breeding habits of the buffalo gnat, it 
will be appreciated that its control is a difficult task. The writer has 
repeatedly recommended that streams inwdiich these insects are breeding 
should be kept as free from debris as possible, including dipping branches 
of overhanging trees and submerged roots. It is possible to do this in 
the immediate vicinity of communities, but prevailing winds may after 
all bring swarms of gnats from a distance. At all events the removal of 
debris from streams lessens the opportunity for them to deposit their 
eggs. Old logs lying crosswise of a stream are a particular menace 
because shallow waterfalls are thus usually produced, hence affording 
ideal breeding places for the gnats. 

To prevent annoyance to beasts of burden some form of spray or 
ointment may be applied. While many repellents are on the 
market, few are of any benefit and practically none affords abso- 
lute relief. Any mixture containing fish oil is of some benefit, but must 
be applied daily. (See also under Hornfly.) Smudges act as good 
repellents, especially burning pyrethrum powder or buhach. Oil of 
citronella applied to the skin and face effectually keeps the insects 
away as long as the parts remain moist with the oil. 

Systematic. — The family Simulidse comprises about seventy-five 
described species (Williston), all in the same genus, i.e. Simulium. 
Two other genera are recognized by Mallock, namely, Prosimulium 
and Parasimulium. The best-known and most widely distributed 
species in America is Simulium pecuarum Riley, the buffalo gnat. 
Riley's description is here given as abbreviated by Garmen : 



148 MEDICAL AND VETERINARY ENTOMOLOGY 

"Male. Eyes meeting and with two sets of facets. Mouth parts soft. 
Head black. Antennae black, with some red. Maxillary palpi black. Thorax 
black above. Abdomen black, with grayish white posterior margins to seg- 
ments. 

"Female. Eyes not meeting. Head gray slate, with short yellow hairs. 
Eyes black, with coppery or brassy reflections. Antennae black with whitish 
pubescence. Thorax grayish slate and generally distinctly marked with two 
mediodorsal and two subdorsal longitudinal black bands. Under side of 
thorax, grayish slate. Abdomen with a broad gray longitudinal band from 
near the base of the second segment, where it is broadest. 

Simulium venustum Say is the black fly, a widely distributed species 
extending from Canada to Texas and from Florida westward. Say's 
description is as follows : 

" Black: thorax, two perlaceous spots before and a larger one behind; 
poisers black ; capitulum bright yellow, dilated. 

"Body black; wings whitish, with yellow and iridescent reflections. 

"Male, eyes very large, separated only by a single line, dull reddish yellow, 
inferior half black; thorax velvet black, a bright oblique, perlaceous, dilated 
line each side before, and a large perlaceous spot or band behind ; sides beneath 
varied with perlaceous; feet, tibia above, and first joint of the four posterior 
tarsi white ; abdomen with an oblique perlaceous line at base, and two approxi- 
mate, lateral, perlaceous ones near the tip. 

"Female, eyes moderate, thorax plumbous-black, immaculate, scutellum 
black, abdomen whitish beneath." 

Simulium meridionale Riley is the turkey gnat, which also enjoys 
wide distribution coinciding with the buffalo gnat. This species at- 
tacks chickens and turkeys, biting the combs and wattles, and is said 
to produce symptoms similar to cholera. 

Riley's description is given by Garmen as follows : 

"The male is from 1.5 to 2 mm. in length, the eyes meeting above, where the 
facets are coarser and of a brilliant coppery luster, those on the ventral side 
smaller and black. Thorax dense black with bluish luster, ventral side grayish. 
Legs reddish with black tarsi. Abdomen above black, posterior margin of 
segments edged with gray. Ventral sides of segments two and three light 
reddish gray, the rest blackish with gray posterior margins. " 

The female is described by the same writer as from "2.5 to 3 mm. long ; the 
head slate-blue, with silvery pubescence; the thorax, with three longitudinal 
lines, the median narrow and widening at the apex, the outer curving in at the 
base and out at the apex ; beneath slate-blue ; abdomen with last five segments 
dark blue above ; segments 2, 3 and 4 each with a black cross bar ; segments 5, 
6 and 7, with two submedian stripes, disappearing on 7 ; bluish white everywhere 
beneath; legs brownish black." 

Simulium occidentale Townsend is perhaps only a variety of the 
turkey gnat and is found in New Mexico. It is described by Town- 
send as follows : 

"This species is smaller than either S. pecuarum or S. meridionale. S. occi- 
dentale differs from S. pecuarum very markedly in the thoracic and abdominal 
markings. These markings are very much like those of S. meridionale; but the 



BUFFALO GNATS AND HORSEFLIES 149 

median thoracic line is always very faint, the abdomen is light fulvous, the 
lateral lines of segments 5, 6 and 7 are curved, and the abdominal markings are 
of a different color, besides other minor differences." 

Simulium columbaczense Schoenbauer is the Columbacz midge of 
Europe, especially abundant in the Valley of the Danube. 



B. Horseflies 
Order Diptera, Suborder Brachycera, Family Tabanidce 

Introduction. — To the family Tabanidae belong the biting flies 
commonly called horseflies, gadflies and deer flies. All the genera be- 
longing to this family consist of large flies (10-25 mm.), the body is heavy 
and the head possesses very large eyes. In the female the eyes are widely 
separate (dichoptic), while in the males the eyes are contiguous (holop- 
tic). The flight is very swift and direct. The antennae (Fig. 28) are 
short (Brachycera) and porrect, consisting of three joints, the third joint 
being annulated ; the arista is absent. The wing venation (Fig. 17) 
is simple and characteristic. 

Larvae. — The larvae (Fig. 1096) are spindle-shaped, tapering at 
both ends ; are eleven-segmented, each segment being clear cut and 
provided with a circlet of tiny spines which aid in locomotion. The 
terminal segment bears a pair of stigmal openings and is somewhat 
prolonged to form a breathing tube. 

Pupae. — The pupae (Fig. 109c; are provided with a conspicuous 
circlet of spines at the apical end of each abdominal segment. 

Breeding Habits and Life History. — The Tabanidse are aquatic or 
semi-aquatic in breeding habits. The eggs to the number of two to three 
hundred are deposited in irregular masses (Figs. 109a-110) on marsh or 
swamp vegetation, for example the leaves of Sagittaria, or on the leaves 
and twigs of trees {e.g. willows) overhanging ponds or sluggish streams. 
In the Sierra Nevada mountains horseflies occur in great numbers at 
elevations of 8000 to 9000 feet, where they breed in the soggy ground 
produced by springs and water from the melting snow. Deer and other 
wild animals suffer terrible torment in the summer time in these locali- 
ties from the bites of horseflies. 

The eggs, covered with a protective secretion, are deposited in 
early and late summer. The larvae hatch in from five to seven days, 
depending on the species, the larger forms requiring somewhat more 
time than the smaller ones. The larvae on hatching fall to the surface 
of the water, penetrate the surface film and then drop to the bottom, or 
if there is no water, the larvae burrow into soft mud. Moisture is cer- 
tainly necessary for their development. Insect larvae, crustaceans and 
other soft-bodied animals provide food for these voracious, carnivorous 
creatures ; cannibalism is also practiced. The larvae grow rapidly during 



150 MEDICAL AND VETERINARY ENTOMOLOGY 




BUFFALO GNATS AND HORSEFLIES 



151 



the rest of the summer and autumn, and very slowly, if at all, during 
the winter. They attain full growth in early spring, crawling out of the 
softer wet mud and into drier earth, where they pupate. The pupal 
period requires from two to three weeks. The emerging flies take refuge 
among the foliage of near-by trees and the females soon begin attacking 
warm blooded animals. The males do not suck blood, but feed on nec- 
tar and other plant juices. Unless swept up with an 
insect net in grass and other vegetation the males 
are seldom seen. 

Bites. — The horseflies have broad blade-like 
mouth parts (Fig. 28) by means of which a deep 
wound is cut, causing a considerable flow of blood. 
The bite is painful and owing to the intermittent 
habits of the flies there is great danger from infection. 

In describing an outbreak of gadflies in Ken- 
tucky, Garmen has the following to say: 1 " Beef 
cattle had lost an average of 100 pounds as a result 
of the constant annoyance from them. ... On 
cattle I counted from ten to nineteen. On mules 
and horses in harness they were a constant annoy- 
ance and even hogs were not exempt. Seven of the 
flies were counted on the exposed side of one of these 
animals lying in a puddle. 

" The persecuted stock appeared to have given 
up fighting their enemies and allowed them to have 
their way. The switch of a cow's tail was observed 
to pass over the backs of clinging flies without 
causing them to move. . . . During the middle of 
the day animals suffered so much that they re- 
frained from grazing at all, either standing close to- 
gether about the barn or else lurking singly in thick- 
ets or standing in pools formed by small streams." 

Relation to Anthrax. — The horseflies are de- 
cidedly intermittent in their biting habits, and inflict a definite lancet- 
like prick from which blood exudes so that the proboscis becomes 
soiled. The flies will bite sick animals as well as healthy ones, — 
hence the possibility for the transmission of an infectious blood disease 
seems to exist. It is regrettable that so little experimental evidence 
is at hand; however, anthrax is at once thought of, owing to the 
virulence and hardiness of the causative bacillus. 2 




Fig. 110. — A horsefly 
(Ghrysops) in the act 
of oviposition. Note 
also an egg mass 
farther down on 
the leaf. (Photo by 
Hine.) X 1. 



1 Garman, H., 1910. An outbreak of gadflies in Kentucky. Kentucky 
Agricultural Exp. St a., Bull. No. 151. 

2 Mr. M. B. Mitzmain has verbally informed the writer (Feb. 17, 1914) 
that he has successfully transmitted anthrax from artificially infected guinea 
pigs to healthy guinea pigs through the agency of both Tabanus striatus and 
Stomoxys calcitrans. A preliminary account of these experiments is in the Journal 
of Tropical Medicine and Hygiene (London), Vol. XVII, No. 4. 



152 MEDICAL AND VETERINARY ENTOMOLOGY 



Anthrax, also known as malignant pustule or carbuncle, wool sorter's 
disease, charbon (French), is caused by Bacillus anthracis. Nearly all 
species of domesticated animals and man are susceptible ; the herbivora 
and rodents are most liable to infection. The mortality may be as high 
as 70 to 90 per cent. 

After the introduction of the organism into the animal the incuba- 
tion period is exceedingly short, i.e. from three to six days. The bacilli 
are seen in the blood stream in advanced cases as chains of rod-shaped 
bodies (Fig. 111). 

Entrance to the body is gained mainly in one ot three ways, 1st, 
through lesions or pricks, i.e. inoculation, producing local anthrax or 

malignant pustule; 2d, by in- 
halation of the spores, produc- 
ing pulmonary anthrax ; and 3d, 
by ingestion with food, producing 
intestinal anthrax. 

Manifestly horseflies could 
only relate directly to the first 
mode of infection (inoculation), 
but it is not altogether improb- 
able that an epidemic of an- 
thrax may thus be started and 
assisted in spreading. Nuttall 
cites Bollinger (1874), who cap- 
tured horseflies on a cow dead 
from anthrax and saw the bacilli 
in preparations made from the 
stomachs and intestines of the 
insects. Two rabbits inoculated 
therewith died of anthrax. Of course, the insects would have to be 
crushed on the animal, and the wound produced by the bite thus in- 
fected in order to produce the disease. 

However, many instances are recorded in which apparently the 
simple bite of the fly was all that was needed to produce malignant 
pustule in humans. Several reputable physicians have related instances 
to the writer in which this was said to have occurred, notably one case 
in a Western state in which a man was in the act of burying a cow dead 
of anthrax when he was bitten severely in the back of the neck by a 
horsefly and in a few days developed a malignant pustule. Nuttall also 
cites a number of similar instances. 

Relation to Surra. — Surra is a highly fatal disease of horses and 
other susceptible animals, such as the carabao, which latter may evidently 
become chronic carriers. Guinea pigs and monkeys are also highly 
susceptible. The disease is endemic in the Philippine Islands, southern 
Asia, Korea and Madagascar. The causative organism is Trypanosoma 
evansi Steel which resembles the trypanosome of Nagana very closely, 




Fig. 111. — Bacillus anthracis, causative organ- 
ism of anthrax. (Greatly enlarged.) 



BUFFALO GNATS AND HORSEFLIES 



153 



as do the symptoms, i.e. there 
is fever, oedema of the abdo- 
men and genitalia, marked de- 
pression and emaciation. The 
trypanosomes are found in 
the blood and especially the 
lymph swellings from the be- 
ginning of the first symptoms. 
The incubation period is from 
eight to nine days. 

Mitzmain 1 has been suc- 
cessful in transmitting the dis- 
ease from animal to animal 
through the agency of a horse- 
fly, Tabanus striatus Fabr. 
(Fig. 112). > 

In a series of experiments 
in which Tabanus striatus was 
used, he allowed the flies to 
first bite an infected guinea 
pig or horse for not more than 
one minute, usually forty-five 
seconds, and then transferred 
them to a healthy animal 
where they were allowed to 
complete the meal without in- 
terruption. An interruption 
of five seconds to three min- 
utes was necessary to transfer 
the flies from animal to ani- 
mal. The horses and mule 
employed in these experiments ' 
were kept in a screened stable 
for from six to eight months 
previous, and the monkeys, 
guinea pigs and rabbits in 
fly-screened cages for about 
ninety days. In all cases the 
animals were examined fre- 
quently (blood examinations 
made) and declared surra free 
at the time the experiments 
began. 




1 Mitzmain, M. B., 1913. The mechanical transmission of Surra by Ta- 
banus striatus Fabricius. Philippine Journ. of Sci., Vol. VIII, No. 3, Sec. B, pp. 
223-229. 



154 MEDICAL AND VETERINARY ENTOMOLOGY 

Flies bred from eggs were allowed to bite a guinea pig which had 
been inoculated with blood from a carabao which had been infected with 
surra for nearly a year previous to the experiment. Three flies w r ere ap- 
plied individually in tubes to the surra-infected guinea pig and allowed 
to feed from forty-five seconds to one minute and thirty seconds, after 
which they were transferred to a monkey and allowed to feed until 
satisfied, i.e. from five to twenty-one minutes. The first high tempera- 
ture, 40.1° C, occurred on the eleventh day, accompanied by a few 
trypanosomes in the peripheral circulation, increasing in numbers until 
the death of the monkey on the twenty-fifth day. 

Blood from the heart of this monkey was inoculated into a horse and 
two guinea pigs. The latter showed infection on the eighth and ninth 
days respectively, and the horse on the seventh day. Two flies were 
permitted to bite this horse, the insects being interrupted in their 
biting in from forty to forty-five seconds and then transferred to a 
healthy horse where the feeding was completed. This animal showed 
numerous trypanosomes in its circulation on the ninth day. Thus posi- 
tive results were secured in both a monkey and a horse. 

Blood from this newly infected horse was inoculated into a mule, 
two monkeys and two guinea pigs, all of which became infected in due 
season, both monkeys dying on the fourteenth and fifteenth days re- 
spectively. 

A second series of experiments was carried on with captured flies, 
which were allowed to bite the above-mentioned surra horse and later a 
healthy horse, similar feeding methods being observed. This experi- 
ment also proved positive, as did blood inoculations to monkeys and 
guinea pigs. 

In order to eliminate the possibility of hereditary transmission of 
trypanosomes in the flies a further experiment was conducted, in which 
seventy-four flies, hatched from eggs of a fly which had previous to egg 
deposition fed on a surra monkey, were allowed to bite a healthy monkey 
during a period of two weeks with negative results. 

Mitzmain concludes that the " contaminated labellum of the fly does 
not appear to be a factor in the conveyance of infection. The maximum 
length of time that Trypanosoma evansi has been demonstrated micro- 
scopically in the gut of this species of fly after feeding on infected blood 
is thirty hours ; the organisms were found in the fly's dejecta two and 
one half hours after biting the infected animal ; and suspension of flies, 
when injected subcutaneously, were found infective for animals for a 
period of ten hours after the flies had fed on infected blood." 

In a letter to the writer under date of Nov. 18, 1913, Mitzmain states 
that " infection is not transferred by Tabanus striatns later than twenty 
minutes after the infective meal. The longest time I have succeeded in 
inducing flies to transmit was fifteen minutes and all results from twenty 
minutes to forty-eight hours were entirely negative. This despite the 
fact that trypanosomes survive in the intestinal tract of T. striatus for 



BUFFALO GNATS AND HORSEFLIES 155 

a period of thirty hours." Mitzmain believes this horsefly to be the 
principal carrier of surra and that the stable fly, Stomoxys calcitrans, is 
ruled out, which is indeed indicated by the long and careful series of 
experiments conducted by that worker on both species of flies. 

Control. — Inasmuch as the painful bite of the Tabanidse, especially 
if these insects are abundant, makes the life of domesticated animals, 
notably horses, quite unbearable, it is desirable that some repellent 
substance or mechanical means be employed to prevent injury. Effi- 
cient repellents usually contain fish oil, which is disagreeable and in the 
presence of dust produces a very filthy coat ; other materials in use are 
" dips " and these do not as a rule act for more than a few hours at most. 
Furthermore where whole herds of animals are to be treated, this 
method is impracticable. Horse nets afford considerable relief, and 
often avert dangerous " runaways." 

Comparatively little of a preventive nature has been done, except 
for the notable work of Porchinski, reported by Howard. 1 Porchinski 
observed that Tabanids collect in great numbers in the neighborhood 
of humid spots and lower themselves to the surface of pools to drink, 
actually touching the water with their bodies. It occurred to him that 
a covering of kerosene on the water would endanger the lives of the 
insects as they came in contact with the surface. Hence a quantity of 
kerosene was applied to a given pool, with most gratifying results. By 
the third day of the experiment the " pool of death " was covered with 
" floating islands " of dead Tabanids. Porchinski recommends that a 
favorite pool be selected, and that the oil be poured on so that a thick 
uniform layer of oil is formed covering the entire pool. Such " pools of 
death " apparently attract the Tabanids from over a considerable adja- 
cent area. The oil must of course be applied as early as possible during 
the season when the adult flies appear and begin to mate and deposit 
eggs. 

Systematic. The following description of family characters and 
key to the North American Genera is according to Hine, 2 our highest 
authority on the Tabanids. 

"The family Tabanidae includes medium-sized to large insects commonly 
called horseflies, gadflies, deerflies, dogflies, earflies and various other names. 
Usually its members are readily recognized at sight by their form and general 
appearance. 

"The three-jointed antennae with the third joint annulated and without a 
style or arista, the rather large tegulse, and the well-developed pulviliform 
empodia taken together serve to distinguish them from other flies in case of any 
doubt. 

"None of the species are really small; the head is large, larger and hemi- 
spherical in the male, smaller and somewhat flattened in the female. 

1 Howard, L. O., 1899. A remedy for gadflies. Porchinski's recent dis- 
covery in Russia, with some American observations. U. S. Dept. of Agric, 
Div. of Entomology, Bull. 20, N. S. 

2 Hine, James S., 1903. Tabanidse of Ohio. Ohio State Academy of Science, 
Special Papers, No. 5. 



156 MEDICAL AND VETERINARY ENTOMOLOGY 

"The antennae are porrect and composed of three segments of which the third 
is compound, having five or eight annulat ions. When there are eight, the basal 
one is only slightly longer than the others, but when there are five, the basal one 
is much longer than any of the others, often longer than all the others combined. 

"The eyes are separated in the female and contiguous in the male. They 
have an area of enlarged facets above in the latter sex, and in life are marked 
with green and purple markings in both sexes. In dry specimens these mark- 
ings are lost, but may be partially restored bjr moisture. Ocelli are present in 
some species and absent in others; and the occiput is flat or concave. The 
proboscis projects and in some species is much elongated; the maxillary palps 
are large and two segmented. 

"The thorax and abdomen are clothed with more or less hair, but no spines 
or bristles. The wings are rather large and encompassed by the marginal vein, 
two submarginal and five posterior cells present, basal cells elongate, anal cell 
usually and sometimes some of the posterior cells closed. Tegulae always promi- 
nent. Legs ample : pulvilli moderate ; empodia developed pulviliform ; middle 
tibia with spurs at the tip. 

"Abdomen composed of seven visible segments, broad, never constricted.' ' 

KEY TO THE NORTH AMERICAN GENERA OF TABANID.E 

(after Hine) 

1 . Hind tibiae with spurs at the tip, sometimes small 2 

Hind tibia without spurs 6 

2. Third segment of the antenna composed of eight annuli, the first of which is 

only a little longer than the following ones 3 

Third segment of the antenna composed of only five annuli, the first of which 
is much longer than any of the following ones ; ocelli present .... 5 

3. Front of female narrow; ocelli present or absent; fourth posterior cell at 

least open Pangonia 

Front of fern ale broad with a large denuded callus; ocelli present ... 4 

4. Eyes in the female acutely angulated above ; wing in both sexes with a dark 

picture Goniops 

Eyes in the female not acutely angulated above ; wings hyaline in both sexes 

Apatolestes 

5. Second segment of the antenna about half as long as the first ; eyes in life 

with numerous small dots Silvius 

Second segment of the antenna as long or but little shorter than the first ; 
wings with a dark picture Chrysops 

6. Third segment of the antenna without, or with a rudimentary basal 

process 7 

Third segment of the antenna with a well developed basal process Tabanus 1 

7. Front of female as broad as long, the callus transverse .... Hcematopota 
Front of the female narrow Diachloms 

A description according to Hine of a few of the commoner species is 
here included. 

(1) Tabanus atratus Fabricius, the black horsefly (Fig. 113), is from "16-28 
mm. in length. The male and female of this common species are easily as- 
sociated as they differ only in sexual characteristics. The whole insect is 
uniformly black and the thorax and abdomen in well-preserved specimens are 
thinly covered with a whitish dust which is easily rubbed off when the specimens 
are not properly cared for. 



Including Atylotus and Therioplectes. 



BUFFALO GNATS AND HORSEFLIES 



157 



" It cannot be confused with any other species recorded, but the smaller 
specimens resemble wiedemanni very closely. The wider front, the longer 




Fig. 113. 



The black horsefly (Tabanus atratus) ; male at left, female at right. 
(Photo by Hine.) 



X 1.5. 



basal process of the third antennal segment and the shape of the frontal 
callosity, which is square in wiedemanni and wider than high in atratus, are dis- 
tinctive characters. Its much larger 

size and less shining color distinguish 
it from lugubris" 

(2) Tabanus stygius Say is the 
black-and-white horsefly. "Length 
20-22 mm. Third segment of the 
antennae red at base, blackish at apex, 
first and second segments and palpi 
dark ; legs black, often the tibia red- 
dish at base ; wings yellowish brown 
with posterior border approaching 
hyaline, a brown spot on the bifurca- 
tion of the third vein, also the trans- 
verse vein closing the discal cell 
margined with brownish; abdomen 
uniform black. 

" Female : Thorax dorsally plainly 
whitish pollinose with more intense 
longitudinal lines. 

" Male : Thorax dorsally uniform 
grayish brown in well-preserved speci- 
mens." 

(3) Tabanus punctifer 0. S. is also 
a black-and-white horsefly (Fig. 114) 
resembling T. stygius, except that it 
has the front tibia? white on the 
basal third and the thorax uniformly 
white in both sexes. 

(4) Tabanus costalis Wied., the green head, is one of the most-dreaded stock 
pests. "Length 12-14 mm. Palpi yellowish, antenna? brownish with the 




Fig. 114. — A black-and-white horsefly (Ta- 
banus punctifer) common in California. X 2. 



158 MEDICAL AND VETERINARY ENTOMOLOGY 



annulate portion darker; thorax including the scutellum uniformly grayish 
yellow pollinose; legs largely black, base of front tibiae and the middle and 
hind tibiae except at apex yellowish ; wings hyaline with the costal cells yellow- 
ish, veins yellowish ; abdomen above alternately striped with black and grayish 
yellow. 

" Female : Frontal callosity black, above with a very much narrowed prolonga- 
tion, the part of which adjacent to the callosity is sometimes obliterated leaving 
the upper part as a separate spot. 

" Male : This sex is much like the female and easily associated with it, but there 
is a tendency toward obliteration of the distinct markings of the abdomen, 
the black of the female is replaced by brownish and the stripes may blend so 
that the whole base of the abdomen is practically one color." 

(5) Tabanus lineola Fabr., the lined horsefly (Fig. 115), is also an important 
stock pest. " Length 12-15 mm. Palpi white ; antennae reddish, annulate por- 
tion of third segment darker ; thorax brown 
and gray striped, the latter color not promi- 
nent ; wings hyaline ; legs reddish, apex of the 
front tibia plainly, apexes of middle and hind 
tibiae faintly, and all of the tarsi dark brown ; 
abdomen above brown or black with three 
prominent, gray stripes. 

The males and females of this species are 
easily associated. In the latter sex there is 
sometimes a confusion of colors ; the dark is 
replaced by reddish but the gray mid-dorsal 
stripe is always prominent in all well-pre- 
served specimens." 

(6) Tabanus sulcifrons Macq. is known as 
the autumn horsefly. "Length 18-21 mm. 
Palpi brownish, antennae nearly black with 
the third segment brownish at base; legs 
dark, bases of tibiae darker ; wings with a 
distinct brownish tinge, cross veins at the 
end of the discal cell and bifurcation of the 
third vein margined with brown. 

"Female: front with parallel sides, fron- 
tal callosity shining brown, not quite as wide 
at the front, nearly square and with a linear 
prolongation above. Segments of the abdomen above with prominent gray, 
hind margins which expand into large gray triangles in the middle ; usually a 
black mark on the anterior part of each of the second and third segments at the 
apex of the gray triangle. 

" Male : The division between the large and small facets of the eye prominent ; 
head slightly more convex than in the female but nearly of the same size, colora- 
tion of the whole body the same as in the female." 

(7) Tabanus striatus Fabr. (Fig. 112) is said to be the most prevalent horsefly 
of the Philippine Islands, and is known to be an important carrier of Surra. 
The following description is after Mitzmain (loc. cit.). 

"The male is very distinct from the female, being smaller and having a 
larger head and different color markings. 

"The distinctly clavate palpi are shorter than in the female, only two thirds 
as long as the labium ; they are dirty white and fringed with moderately long 
black hairs. 

"The abdominal color markings take the form of a T of pale cadmium yellow 
in a field of burnt sienna, bordered with pale clay yellow. The area of the large 
facets of the eyes is colored Roman sepia surrounded by an elliptical band of 




Fig. 115. — The "lined' 
{Tabanus lineola). 



horsefly 
X3. 



BUFFALO GNATS AND HORSEFLIES 159 

ultra ash gray. The field of small facets has a mauve fringe bounding an area 
of iridescent mauve and Prussian green. 

"Size : 1-1 to 15 millimeters. 

"Wing expanse : 25 to 28 millimeters. 

"Female: The front is narrow, converges slightly anteriorly; the color is 
golden, marked with a black callosity of irregular form. 

"The head is considerably smaller than that of the male; eyes iridescent 
mauve and Prussian green. 

"The palpi are prominently conical, as long as, or slightly longer than, the 
labium ; the color is the same as in the male, mottled with short black hairs. 

"The abdomen is alternately striped with Cologne earth and pale clay yellow. 
The median stripe is pale clay yellow. In both sexes the thorax is indistinctly 
striped with pale clay yellow and pale brown, and the wings are transparent 
except the costal and subcostal cells which are pale brown. 

"Size: 15 to 17 millimeters. 

"Wing expanse : 26.5 to 29 millimeters." 



CHAPTER XIII 



THE COMMON HOUSE FLY 



Order Diptera, Family Muscidce 
Life History, Habits and Relation to Disease 

Family Muscidse. — The family Muscidae, to which the house fly 
(Musca domestica Linn.) belongs, has the following characteristics : 
" Rather small to moderately large, never elongate, thinly hairy or bare 
flies. Antennal arista plumose to the tip, sometimes above only, and 
rarely bare, in which cases the absence of bristles on the abdomen, 
except at tip, together with the narrowed first posterior cell, characters 
distinctive of the group, will distinguish the flies belonging here from 

their allies. Eyes of the male ap- 
proximated or contiguous ; front 
of female broad. Eyes bare or 
hairy. Abdomen composed of four 
visible segments. Genitalia not 
prominent ' ' ( TVilliston l ) . 

Characterization of the House 
Fly. — Hewitt's 2 description of the 
house fly after Schinir is undoubt- 
edly the best for our purpose, viz. 
" Frons of male occupying a fourth 
part of the breadth of the head. 
Frontal stripe of female narrow in 
front, so broad behind that it en- 
tirely fills up the width of the frons. 
The dorsal region of the thorax 
dusty gray in color with four 
equally broad longitudinal stripes. Scutellum gray with black sides. 
The light regions of the abdomen yellowish, transparent, the darkest 
parts at least at the base of the ventral side yellow. The last segment 
and a dorsal line blackish brown. Seen from behind and against the 
light the whole abdomen shimmering yellow, and only on each side of 
the dorsal line on each segment a dull transverse band. The lower 

1 Williston, S. W., 1896. Manual of North American Diptera. James T. 
Hathaway, New Haven. 

2 Hewitt, C. Gordon, 1910. The House Fly. xiii + 195 pp. The Univer- 
sity Press.. Manchester, England. 

160 




Fig. 



116. — The common house fly (Musca 
domestica Linn.). X 4. 



THE COMMON HOUSE FLY 



161 



part of the face silky yellow, 
shot with blackish brown. 
Median stripe velvety black. 
Antennae brown. Palpi black. 
Legs blackish brown. Wings 
tinged with pale gray with yel- 
lowish base. The female has 
a broad velvety black, often 
reddishly shimmering, frontal 
stripe, which is not broader at 
the anterior end than the 
bases of the antennae, but be- 
comes so very much broader 
above that the light dustiness 
of the sides is entirely obliter- 
ated, the abdomen gradually 
becoming darker. The shim- 
mering areas of the separate 
segments generally brownish. 
All the other parts are the 
same as in the male. Mature 
insect 6-7 mm. in length, 13- 
15 mm. across the wings " 
(Fig. 116). 

Why called House Fly. — 
Out of a total of 23,087 flies 
collected by Howard l in din- 
ing rooms in different parts of 
the country 22,808 or 98 per 
cent of the whole number were 
Musca domestica. Again out 
of a total of 294 flies collected 
by the writer, representing the 
entire fly population of one 
house, 202 or 94.4 pe^ cent 
were Musca domestica. Thus 
the term common house fly is 
not misapplied. Several of 
the commoner species of flies 
found indoors are shown in 
the accompanving illustration 
(Fig. 117). 

Distribution of Sexes. — In 
order to determine the distribution of the sexes, observations were made 

1 Howard, L. 0., 1900. A Contribution to the Study of the Insect Fauna of 
Human Excrement. Proc. Wash. Acad, of Sciences, Vol. II, Dec. 28, pp. 541-604. 




162 MEDICAL AND VETERINARY ENTOMOLOGY 

under two different conditions, viz. first, six sweepings with an insect 
net were made over a horse-manure pile on which many flies had gathered 
(the results are shown in Table VI) ; second, all but half a dozen flies 
were collected in one house, giving a fairly representative lot for in- 
doors, even under screened conditions (Table VII) . 

TABLE VI 

Showing Results with Regard to Sex and Species in Six Sweepings 
from a Horse Manure Pile on May 19, 1909 



House fly (Musca do- 
mestica) . . . . 
Muscina sp. . . . 
Blowfly (Calliphora 

sp.) 

Lucilia cozsar . . , 
Other species . . , 
Totals 



FlKST 



2 
153 

6 

2 

1 
4 



12 126 



Second Third 



d ? 

4 81 
7 



1 

1 

4i2 



9416 71 



Fourth 



? 

77 
5 


1 

2 



15 85 



Fifth 



d ? 

4 210 

3 10 





4 2 



11 222 



Sixth 



d V 
5 112 
1 4 



116 



Total 



d- ? 

32 697 

8 37 

3 3 

4 

13 13 



56 754 



TABLE VII 

Showing Number of Individuals Collected in a Screened Dwelling 
June 1, 1909, Representing the Entire Fly Population of the Same 

$ 9 

House fly {Musca domestica) 86 116 

Muscina sp 3 1 

Homalomyia sp 5 

Calliphora sp '. . . . . _1 2 

Totals 95 119 



Explanation and Comparison of Tables VI and VII. — These two 
tables give us some information as to the relative abundance of the 
house fly, and the distribution of the sexes. Table VI shows clearly that 
of those flies which frequent both the manure pile and the home, the 
house fly (Musca domestica) composes 90 per cent, and that of the total 
collected, over 95 per cent (95.4 per cent) were females. Thus, it is clear 
that it is the "instinct" to oviposit (to lay eggs) that has mainly attracted 
these insects to the manure. In fact, fresher parts of the manure pile 
are often literally white with house-fly eggs in countless numbers. Ob- 
servations made in the near vicinity of the manure piles proved that 
certainly the same percentage (over 95 per cent) of the flies clinging to 
the walls of the stable, boxes and so on were males. 

That the number of males and females in the house fly is normally 
about equal is evidenced by the fact that of a total of 264 pupae collected 
indiscriminately and allowed to emerge in the laboratory, 129 were males 



THE COMMON HOUSE FLY 



163 



and 135 were females. The author has, however, made observations 
on certain flesh flies, Lucilia coesar Linn, and Calliphora wmitoria Linn., 
which indicate that the factor of underfeeding must be considered in this 
connection. From a large amount of unpublished data, it is evident 
that underfeeding results in the emergence of a greater percentage of 
males. This does not imply, however, that sex is influenced by feeding ; 
it only indicates that cutting short on food supply destroys the larval fe- 
males first. Feeding experiments, not yet complete, on the house fly 
indicate that the same holds true here, but also that this insect is not so 
plastic as the flesh fly, hence does not vary so greatly in size and dies 
more easily when underfed. 



■ , ■; v 


i 


• ik- 


s 





Fig. 118. 



Life history of common house fly. (a) eggs ; (b) larva ; (c) pupa 
(d) imago or adult. X 2. 



Of the total number of house flies (202) collected indoors (June, 1909), 
representing all but perhaps six of the total number in that particular 
house, 57 per cent were females, showing nearly equal distribution for 
the sexes. This would, it seems, indicate that males and females are 
equally attracted to the house by odors issuing therefrom. 

Life History. — The house fly passes through a complex metamorpho- 
sis (Fig. 118), i.e. egg, larva (maggot), pupa (resting stage) and imago 
or full-grown winged insect. 

From 75 to 150 eggs are deposited singly, piling up in masses, and there 
are usually several (2 to 4) such layings at intervals of three or four days. 
Female flies begin depositing eggs from nine to twelve days after emerg- 
ing from the pupa case. Excrementous material, especially of the horse 
(Figs. 119-120), is the favorite material upon which the eggs are deposited 
and upon which the larvae feed. Other suitable situations are kitchen 



164 MEDICAL AND VETERINARY ENTOMOLOGY 

refuse, brewer's grain and other decaying vegetable matter. Where the 
city garbage is carefully disposed of with only ordinary attention to horse 




Fig. 119. 



A typical rural fly breeding place, — the everlasting manure pile. The prin- 
cipal menace is the fresh, warm manure added on top daily. 



piljM 








. | i 




. ■■■■ 








|F* 




■*' 




*** ■ . .^ 


- . >. *. .. ^ 


fe- 


| tit * - " " c T" ' 






IH 


-.>r 




" *»■■" i. 


- -■>**. - -- ;*V «£. - ' j 




• . "■ -. 




% v --Itf 





















Fig. 120. — Fly maggots will be found in abundance in similar manure piles. This^is 
surely not sufficiently ornamental to maintain indefinitely, nor will it improve the 
health of the neighbors. 



manure, it seems quite safe to say that 95 per cent of the house flies are 
bred in the latter. The house fly does not breed as abundantly in cow 
manure, although plentifully enough to take such material into con- 



THE COMMON HOUSE FLY 165 

sideration, especially when it occurs in piles mixed with straw. The 
eggs of the house fly hatch in from twelve to twenty-four hours; the 
newly hatched larva? begin feeding at once and grow rapidly. 

To gain an estimate of the number of larvae developing in an average 
horse-manure pile, samples were taken after four days' exposure to flies, 
with the following results : first sample (4 lbs.) contained 6873 larva? ; sec- 
ond sample (4 lbs.), 1142; third sample (4 lbs.), 1585; fourth sample (3 
lbs.), 682 ; total 10,282 larvae in 15 pounds. All of the larvae were quite 
or nearly full grown. This gives an average of 685 larvae per pound. 
The weight of the entire pile was estimated at not less than 1000 pounds, 
of which certainly two thirds was infested. A little arithmetic gives us 
the astonishing estimate of 455,525 larvae (685 X 665), or in round num- 
bers 450,000, i.e. about 900,000 larvae per ton of manure after only four 
days' standing. This particular manure pile (not from a livery stable, 
either) was only one of many known to exist in various parts of the city. 
No wonder flies fairly swarm in the vicinity of these choice ornaments ! 

The larval stage is the growing period of the fly, and the size of the 
adult will depend entirely upon the size that the larva attains. An 
underfed larva will result in an undersized adult. The growing stage 
requires from four to six days, after which the maggots often crawl 
aw r ay from their breeding place, many of them burrowing into the loose 
ground just beneath the manure pile, or under boards or stones, or into 
dry manure collected under platforms and the like. (One and three 
fourths pounds of dry manure, taken from beneath a platform, contained 
2561 pupae). The larvae often pass three or four days in the prepupal 
or migrating stage before actually pupating ; but in a given set of in- 
dividuals under similar conditions the various stages are remarkably 
similar in duration, — when one pupates, the rest will certainly follow 
in short order, and when one emerges, others quickly appear. The aver- 
age time required for development from the egg to the imago is differently 
estimated by various observers, inasmuch as temperature greatly in- 
fluences the time required. Packard (1874) gives the time at from ten 
to fourteen days, Howard (1906), at Washington, D.C., as ten days. In 
Berkeley, California, where the weather is uniformly cool (rarely above 
80° F. and a mean of 48° F. during the winter months), the life cycle 
is completed usually in from fourteen to eighteen days, less often in 
twelve days. At a maintained temperature of 30° C. the minimum 
time required for complete metamorphosis is nine and one third days. 
Prolonged cool weather or artificially cooled environment results in 
greater retardation. Even allowing for such retardation, the number of 
generations produced during the summer is quite large, and in California 
(Berkeley) I have seen house flies emerging from their breeding places 
during every month of the winter season. This latter fact lends even 
greater importance to a house-fly campaign. In early March a veritable 
pest of flies was encountered while on a trip through the Imperial 
Valley (California). 



166 MEDICAL AND VETERINARY ENTOMOLOGY 




Fig. 121. — Illustrating 
the effect that under- 
feeding the larva has 
on the size of the 
adult fly (Luc ilia cce- 
sar). Overfeeding, if 
it does not result fa- 
tally, does not increase 
the size of the fly over 
the optimum, as may 
be seen by the upper- 
most individual, which 
is the same size as the 
next lower individual 
or optimum. Each of 
the next lower individ- 
uals is the result of de- 
creasing the time of 
feeding by six hours. 
These results are based 
on a large number of 
individuals in each 
case. X 1. 



When the fly emerges from the pupa case with 
fully developed wings, it is as large as it will ever 
be, except in expansion and addition in weight, 
due to stomach contents or development of eggs 
in the female. This explains why no young house 
flies are seen (young in the sense of being small). 
The little flies upon the windows are not " baby " 
flies, but belong to another species, also adult. 
One can easily influence the size of a fly by un- 
derfeeding it in the larval stage, as illustrated in 
Fig. 121 (see Herms, 1 1907). The question has 
been asked, " Why are all house flies so nearly of 
one size? " This is not altogether true. There 
are some undersized house flies, but the great 
majority of the larvae or maggots find ample food 
for optimum development. Furthermore, experi- 
ments show that the house fly is not as plastic in 
respect to food conditions as the flesh fly ; in other 
words, larvae which are underfed perish easily. 

House flies reach sexual maturity in three or 
four days and begin to deposit eggs on the ninth 
day after emergence from the pupa. Sunshine 
stimulates their breeding habits. 

Estimating that one adult fly deposits from 
120 to 150 eggs with at least six lots at intervals 
of from three to four days, Hodge 2 gives us the 
following astounding statement: "A pair of flies 
beginning operations in April may be progenitors, 4 
if all were to live, of 191,010,000,000,000,000,000 
flies by August. Allowing one eighth of a cubic 
inch to a fly, this number would cover the earth 
47 feet deep." 

- Influence of Temperature on Life History. — 
While conducting an extensive series of experi- 
ments in which many hundreds of house flies 
were used in all stages, a record was made of the 
temperature at which the containers were kept. 
Ordinarily not more than one to three quarts of 
manure were used for the growing maggots, hence 
the temperature of the environment did not differ 
widely from that of the manure. The temperature 



1 Herms, W. B., 1907. An Ecological and Experi- 
mental Studv of Sarcophagidse. Journ. Exp. Zool., Vol. 
IV, No. 1, pp. 45-83. 

2 Hodge, C. F., 1911. Nature and Culture, July, 
1911. 



THE COMMON HOUSE ELY 167 

of an average manure pile to which material is added daily varies 
from 18° C. to 66° C. Young growing larvae are most numerous at tem- 
peratures varying from 45° to 55°. Below 45° half-grown and full-grown 
larvae occur and above 55° the temperature seems to become too great. 
From the following table it will be seen that temperature influences 
the time required for the development from egg to imago very materially, 
but nevertheless with an average outdoor temperature of 1S° C. flies 
ordinarily require only from twelve to fourteen days to pass through 
the same stages ; this is of course due to the higher temperature of 
the manure pile, as already indicated above. The shortest time required 
for complete metamorphosis is seen to be nine and one third days. 

TABLE VIII 

Showing Influence of Temperature on the Length of Life History 
of musca domestica 

The insects were kept at the temperature indicated from egg to emergence 
of the imago. The average temperature is here given, the variation from 
the average was probably not more than ± 1°. Temperature of the air 
and not of the manure is here considered. 





16° C 


18° C 


20° C 25° C 


30° C 




Min. Max. 


Min. Max. 


Min. 


Max. Min. 


Max. 


Min. 


Max. 


Egg stage . . . 

Larval stage . 

Pupa stage . . 

Total time re- 
quired from egg 
to imago . . 


36 hrs. 40 hrs 
11 ds. 26 ds. 
IS ds. 21 ds. 

40* ds. 4S| ds. 


27 hrs. 
10 ds. 
12 ds. 

23| ds. 


30 hrs. 

14 ds. 

15 ds. 

30i ds. 


20 hrs. 

8 ds. 

10 ds. 

18| ds. 


30 hrs. 

10 ds. 

11 ds. 

22i ds. 


12 hrs. 
7 ds. 
7 ds. 

14| ds. 


20 hrs. 

8 ds. 

9 ds. 

17| ds. 


8 hrs. 
5 ds. 
4 ds. 

9 ids. 


12 hrs. 
6 ds. 
5 ds. 

11| ds. 


Average time re- 
quired to de- 
velop from egg 
to imago . . 


44.8 days 


26.7 days 


20.5 days 


16.1 days 


10.4 days 



Other Breeding Places. — Stable yards and empty town lots used for 
horses are often a source of many flies. Here the droppings from the 
horses accumulate and are kept moist by urine, thus affording good 
breeding places (Fig. 122). The stable yard and town lot used for horses 
must not be overlooked in the campaign against the house fly. Merely 
sweeping up the manure with a broom after the removal of the manure 
pile or superficial shoveling without scraping up the loose earth will not 
remedy the matter entirely. It must be borne in mind that when the 
larva? have fed sufficiently for full growth, that is. from four to five days, 
they crawl into the loose earth underneath the manure pile (often great 
pockets of larva? may be found thus), or they wander to loose debris in 
the immediate vicinity ; many, of course, remain in the drier portions 
of the manure pile to complete their life cycle. Thousands of pupae 



168 MEDICAL AND VETERINARY ENTOMOLOGY 

(recognized as chestnut-colored, barrel-shaped objects) were taken by 
the writer in one instance from beneath a platform leading into a 
stable. Therefore, when cleaning up, such conditions and situations 
must also be taken into account. 

Human excrement, if left uncovered, furnishes another good breeding 
ground for the house fly. Indiscriminate defecation in alley ways and 
out-of-the-way places should be considered a misdemeanor punishable by 
a heavy fine, for the reason that house flies may breed in human excre- 
ment, and especially because of the very great danger of disease transmis- 
sion by the flies. In communities where there is no sewer system, sanitary 
fly-tight privies should be required by ordinance (see next chapter). 

Where dairy cattle are fed on brewer's grain the waste is usually 




Fig. 122. — A manure-covered corral kept moist by urine from the horses forms an im- 
portant breeding place for both house flies and stable flies. 

thrown away in small heaps in a near-by field, thus affording a famous 
breeding place for flies. The writer has found that such conditions 
often explain the great abundance of flies about certain certified dairies, 
otherwise in excellent condition. All wastes of this kind should be 
spread out thin so that the material dries out quickly, thus preventing 
the development of flies. 

Guinea pig pens, rabbit pens and chicken coops may become prolific 
breeders of flies if they are not carefully cleaned. 

Kitchen refuse (Fig. 123), decaying fruit, garbage dumps, in fact 
any organic material that is beginning to decompose, — all afford 
breeding places for the house fly. But the source of the fly as a real 
nuisance is essentially the horse-manure pile. 



THE COMMON HOUSE FEY 169 

Range of Flight. — Ordinarily under city conditions it may 
be safely said that where flies are abundant they have been bred 
in the same city block or one immediately adjacent. The house 
fly can, however, use its wings effectively and may be carried by 
the wind, though it usually seeks protection very quickly when a strong 
breeze blows. Where houses are situated close together flies have the 
opportunity to travel considerable distances by easy flights and they 
are often carried on meat and milk delivery wagons, animals, etc. 

In a most illuminating experiment by Copeman 6 et al., it has been 
shown that house flies may invade a community at a distance of from 300 
yards to 17,000 yards from their breeding place ; in this case a refuse heap. 

Longevity of Flies. — In order to determine the longevity of flies 




Fig. 123. — A poor excuse for a fly-tight garbage can. This should be regulated by 

ordinance. 

it is necessary to keep the same individual under observation from the 
time of emergence from the pupa to the time of death. The writer has 
done this by keeping each pupa in a separate vial, noting the time of 
emergence to the hour and spotting each fly lightly with Chinese white 
dorsally on the thorax. The spots can be arranged singly and in com- 
bination so that many different flies can be kept under observation at 
the same time. After marking, the flies were liberated in bobbinet- 
covered cages (size of cages never more than 8" X 10" X 18"). Each 
cage was provided with sugar water and a receptacle of horse manure. 
A full set of experiments under sufficiently varying conditions indicate 
an average life of close to thirty days with a maximum life of something 

1 Copeman, Howlett and Merriman, 1911. In reports to the local Govern- 
ment Board of Public Health and Medical Subjects. New Series No. 53, Report 
No. 4 on Flies as Carriers of Infection (London). 



170 MEDICAL AND VETERINARY ENTOMOLOGY 

over sixty days during the summer months., In hibernation flies may 
live over winter, i.e. from October to April, which is the case in our 
Eastern and Central states. In California, flies emerge from their 
pupa cases throughout the winter, and their life history is then con- 
siderably longer than in summer. 

Dusting flies with foreign substances for longevity experiments is not 
satisfactory, inasmuch as they easily succumb to its effects or are cer- 
tainly not normal. 

Relation to Light. — In determining methods of control the normal 
behavior of organisms under natural stimuli should be taken into ac- 
count and applied wherever possible. The better acquainted we are with 
the normal behavior of any organism, including the life history, the 
better able are we to cope with it. 

The larvse of the house fly when normal respond negatively to light 
upward of .00098 CM., i.e. crawl away from the source of light and into 
darker areas. This reaction is useful to the larva? because light and its 
heating or desiccating effect is injurious both directly and indirectly, — 
the latter because sunlight dries out the food material (manure) unless 
heaped up, and dry manure is unfavorable for the growth of the larvae. 

On the other hand, the adult flies respond positively to light, going 
toward the source of light. This reaction is less pronounced in the 
females, as maybe seen from the following table (Table IX). 

TABLE IX 

Showing the Response of Adult House Flies to, Light, under Various 

Intensities 

The source of light in all cases was. an incandescent lamp ; the several inten- 
sities were secured by means of diaphragms in a low-intensity dark box 
such as has been described by the author (loc. cit. 1911). 



Intensity Sex 


No. op 

Trials 


Average 
Time Re- 
quired FOR 
Response 


Per Cent 
op Re- 
sponses 

UNDER 

Three 
Seconds 


Ch 

I 

Tow- 
ard 


\RACTER OF 

lESPONSE | PeECENTAGE 

! op Positive 
Reactions 
Away Indiff. 


256 C. M. both 
.2533 C. M. male 
.2533 C. M. female 
.0633 C. M. 1 both 


25 
50 
50 

50 


55.4 sec. 

8.86 sec. 

25.44 sec. 

24.68 sec. 


32% 
62% 
50% 
26% 


19 

58 
44 
41 


6 
2 

2 
3 




4 
6 


76% 

97% 
88% 
82% 



From the above table it must be concluded that the house fly responds 
positively to light (goes toward the source of light) , even in very low in- 
tensities, at least as low as .0055 C. M. and that the male is far more re- 
sponsive to this stimulus than is the female. 

The female is less reactive to light and more reactive to chemical 



THE COMMON HOUSE FLY 171 

stimuli such as odors, which enable her to find the proper place for the 
deposition of eggs and food for the larvse. Because of the more or less 
pronounced relation to light, manures deposited in dark places are less 
likely to breed flies. Flies can commonly be observed coming to rest 
in sunny spots in preference to shade, shunning the shadows. 

Large areas of light are always preferred to small areas of light even 
though the intensity is the same. The following experiment is evidence. 
Two areas of light with a ratio of 1 : 3000 and a light intensity of 7.25 
candle meters were placed opposite each other at a distance of one meter, 
the experimental room being otherwise completely darkened and 
painted dead black. Fifty flies were tested, giving each fly five trials 
midway between the light areas. Out of 250 trials 149 were toward the 
larger area, 93 toward the lesser and 8 were indifferent, i.e. 59.6 per cent 
toward the larger. This experiment shows that the flies respond posi- 
tively to light and select the larger area by preference. Whether this 
indicates a degree of image-forming powers or not need not be con- 
sidered here, but the writer * has found that certain flesh flies also re- 
spond more readily to the larger area, that is a response of 74 per cent, 
and Cole 2 found that the mourning cloak butterfly shows a response of 
87.2 per cent. 

The response to light can be made use of in a practical way, first by 
placing the stable manures in which the flies breed in darker portions of 
the stable so that the light reactions of the flies will take them away 
from the manure and toward the source of light ; secondly, manure 
boxes should be so constructed that flies finding their way into the box 
or developing therein are afforded an opportunity to fly toward a light 
opening which leads into a fly trap. 

Economic Considerations. — Aside from the loss of life, through 
typhoid fever and diseases carried wholly or in part by the fly, an economic 
loss of importance, the annual loss to civilized man through the direct 
agency of the house fly must reach astonishing proportions. Dr. L. O. 
Howard estimates the cost of screening at over ten millions of dollars 
per annum for the United States, and the writer has estimated the cost 
of fly traps, sticky fly paper and fly poison at more than two millions of 
dollars annually. If this enormous amount were spent during only one 
year in controlling the fly at the right end of its life history, a second 
year would find a saving of several millions of dollars, not to mention 
the lives that have been spared and the comfort wrought. 

Relation to Disease. — We should be familiar with the actual method 
of disease transmission by the house fly. Some insects, as already 
described, act as intermediate host for pathogenic organisms, which 

# ' Herms, W. B., 1911. The Photic Reactions of Sarcophagid Flies, es- 
pecially Lucilia ccesar Linn, and Calliphora vomitoria Linn. Journ. Exp. Zool., 
Vol. X, No. 2, pp. 167-226. 

2 Cole, Leon J., 1907. An experimental study of the image-forming powers 
of various types of eyes. Proc. Amer. Acad. Arts & Sci., Vol. 42, No. 16, pp. 
335-417. 



172 MEDICAL AND VETERINARY ENTOMOLOGY 



latter cannot exist sexually and be transmitted without the insect, e.g. 
the malarial fever parasite {Plasmodium vivax and other species), which 
passes part of its life history in the body of the Anopheles mosquito. 
The house fly, as far as known, is not an intermediate host necessary to 
the life of a pathogenic organism of humans, but is by accident of habit 







Fig. 124. — Head of the common house fly, front view. (Much enlarged.) 

and structure one of the most important and dangerous of disease-trans- 
mitting insects. In habit the house fly is revoltingly filthy, feeding 
indiscriminately on excrement of all kinds, on vomit and sputum, and 
is, on the other hand, equally attracted to the daintiest food of man, 
and will, if unhindered, pass back and forth between the two extremes. 






THE COMMON HOUSE FLY 



173 



The house fly's proboscis (Fig. 124) is provided with a profusion of fine 
hairs which serve as collectors of germs and filth ; the foot (Fig. 125) 
of the fly when examined under the microscope presents an astonishing 
complexity of structure. Each of the six feet is equally fitted with bristly 
structures and pads, which latter secrete a sticky material, adding thus 
to the collecting powers. This structural condition, added to the natural 
vile habits of the house fly, completes its requirements as a transmitter 
of infectious diseases of certain types. 

This creature has long been known to contaminate food, but has, 
nevertheless, been regarded as a scavenger, and thus as a real servant 




Fig. 125. — Foot of the common house fly. (Much enlarged.) 



of man ; but if there remains any doubt in the mind of the reader, after 
reading what follows, as to the necessity of getting rid of this wolf in 
sheep's clothing, let him take the time to make a few careful observations 
for himself. 

Circumstantial evidence against the house fly as a transmitter of 
such infectious diseases as typhoid fever, tuberculosis, dysentery and 
cholera, is complete as summed up thus: First, it possesses the best 
possible structures for the conveyance of " germs " and filth ; second, 
it possesses the habit of feeding on excrement, vomit and sputum ; third, 
the causative organisms (" germs ") of the above-named diseases may 
be present in the matter mentioned in the second clause; fourth, 
the house fly is the principal fly found in dwellings, alighting on the 
prepared food of man, or on food products in grocery stores, fruit stands 
and meat markets. 

Experimental evidence that the house fly actually does carry bacteria 
on its mouth parts and feet and in its intestinal tract is not wanting. 
To illustrate, the following simple experiment may be cited. 



174 MEDICAL AND VETERINARY ENTOMOLOGY 



In order to show that the house fly (Musca domestica) can carry 
" germs " of a known kind, a partially sterilized fly was placed in a test 
tube containing a culture of Staphylococcus aureus. After walking about 
in this tube and becoming contaminated with the Staphylococci, the fly 
was transferred to a sterile agar-agar plate upon which it was allowed to 
crawl about for three minutes. The plate was then incubated for twenty- 
four hours, after which it was examined and photographed (Fig. 126). 
The photograph shows the trail of the fly as it had walked about. 

Every place that the 
foot touched is plainly 
marked by a vigorous 
bacterial growth. 
That the fly cannot 
easily get rid of all 
the bacteria on its 
feet is also illustrated 
by this photograph, 
inasmuch as three 
minutes spent crawl- 
ing about on the agar 
plate did not appar- 
ently lessen the 
growth-vigor of bac- 
teria deposited, and a 
second plate of agar- 
agar contaminated by 
the same fly immedi- 
ately after exposure 
of the first plate gave 
equally astonishing 
results. The same 
experiment was per- 
formed, using Bacillus prodigeosus with even more pronounced results. 
These experiments were repeated several times with like effect. 

A second series of experiments was carried on as follows : During 
the middle of May (1909) house flies were captured in various parts 
of Berkeley, placed at once in sterilized vials, and in the laboratory 
placed under bell jars with agar-agar plates, all under sterilized con- 
ditions. After the flies had crawled about on the culture media, the 
latter were incubated for twenty-four hours. In every case but one 
a strong growth of bacteria appeared. This one was incubated longer 
and after forty hours four centers of infection appeared. This fly had 
been taken on a sunny wall on one of the main streets, and having 
been under observation in this position for a long time (as reported by 
the assistant) it was first supposed that the action of the sunlight had 
sterilized it. This series of experiments included flies taken from a 




Fig. 126. — Cultures of Staphylococcus aureus transferred 
by a house fly to a sterile agar-agar plate upon which it 
was allowed to crawl for. three minutes. Incubation 
period, 24 hours. 



THE COMMON HOUSE FLY 175 

number of situations, namely, principal thoroughfares, sunny walls, 
street corners, manure piles and the dining room. Without excep- 
tion the flies were laden with bacteria, and in all cases the greatest care 
was exercised not to introduce accidental infection to the culture plates. 

Probably the most accurate study of these factors was carried on 
by Esten and Mason x on the Sources of Bacteria in Milk and certainly 
most striking facts were revealed. The following table (Table X) and at- 
tached remarks are taken from that publication, and need no further 
comment or explanation. 

" From the following table the bacterial population of 414 flies is 
pretty well represented. The domestic fly is passing from a disgusting 
nuisance and troublesome pest to a reputation of being a dangerous 
enemy to human health. . . . The numbers of bacteria on a single fly 
may range all the way from 550 to 6,600,000. Early in the fly season the 
numbers of bacteria on flies are comparatively very small, while later the 
numbers are comparatively very large. The place where flies live also 
determines largely the number that they carry. The average for 414 
flies was about one and one fourth million bacteria on each. It hardly 
seems possible for so small a bit of life to carry so large a number of 
organisms. . . . The objectionable class coliaerogenes type was two 
and one half times as abundant as the favorable acid type." 

From the experiments previously cited it may be seen that the fly 
becomes infected by walking over infective materials, both its feet and 
wings becoming contaminated. The intestinal contents of flies become 
infected by feeding on infective material, and bacteria are dejected in 
the fly " specks." It furthermore seems plausible that flies might be- 
come infected in the larval stage by developing in fecal matter and that 
the newly emerged flies would already be dangerous. Under experi- 
mental conditions Graham-Smith 2 has produced infected blowflies 
by feeding the larvae on meat infected with spores of Bacillus anthracis. 
He found that the blowflies remained heavily infected for at least 
two days after emerging and that the bacillus could be cultivated either 
from the limbs or intestinal contents of the flies more than fifteen or 
nineteen days old. 

Human foods are infected by flies primarily by direct contact through 
the touch of feet, proboscides and wings ; and secondly, through fly 
" specks " (feces) ; and finally, flies grossly infect liquids by accidentally 
dropping into the fluid, — this is especially true of milk. 

The opportunity for flies to become infected is so great in all com- 
munities, even the most sanitary, that no fly should be trusted to alight 
on food prepared for human consumption. The following quotation 

1 Esten and Mason, 1908. Sources of Bacteria in Milk. Storrs Agric. Exp. 
Sta.,Bull. No. 51. 

2 Graham-Smith, G. S., 1911. Further observations on the ways in which 
artificially infected flies carry and distribute pathogenic and other bacteria. 
Reports of the local Government Board on Public Health and Medical Subjects. 
(New Series No. 53.) Further Reports No. 4, pp. 31-48. 



176 MEDICAL AND VETERINARY ENTOMOLOGY 





















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THE COMMON HOUSE FLY 177 

from Nuttall, 1 whose careful judgment is here considered, is directly 
to the point, viz. : "It should be remembered that a fly may cause rela- 
tively gross infection of any food upon which it alights after having fed 
upon infective substances, be they typhoid,' cholera or diarrhea stools. 
Not only is its exterior contaminated, but its intestine is charged with 
infective material in concentrated form which may be discharged un- 
digested upon fresh food which it seeks. Consequently, the excrement 
voided by a single fly many contain a greater quantity of the infective 
agents than, for instance, a sample of infected water. In potential 
possibilities the droppings of one fly may, in certain circumstances, weigh 
in the balance as against buckets of water or of milk ! " 

That flies may serve as carriers of disease has long been suspected, 
e.g. : "Mercurialis (1577) considered that they carried the virus of plague 
from those ill or dead of plague to the food of the healthy. Sydenham 
(1666) remarked that if swarms of insects, especially house flies, were 
abundant in summer, the succeeding autumn was unhealthy. A number 
of authors, e.g. : Crawford (1808), might be cited who refer in a general 
way to insects, especially house flies, as carriers of infection ; Moore 
(1853) refers to flies as possible carriers of cholera, typhoid, tuberculosis, 
anthrax and leprosy; Leidy (1872) refers to flies as carriers of the in- 
fection of hospital gangrene and of wound infection " (quotation from 
Nuttall, 1909, loc. tit.). 

Typhoid Fever. — The causative organism {Bacillus typhosus) of 
typhoid fever belongs to the typhoid-dysentery group, and is found 
outside the human body " only in those situations where it could be 
more or less directly traced to an origin in the discharge of a typhoid 
patient or convalescent." Jordan 2 and others have shown that the 
life of this germ in the water of flowing streams is of comparatively 
short duration, and that multiplication does not ordinarily take place 
in water; indeed, a steady decline in numbers goes on. Infection 
caused by transmission through the air is exceedingly rare according 
to these authors, but soil on the contrary may become contaminated 
through buried human excrement, or otherwise, and continue to be a 
source of infection for a much longer time than water. Notwithstanding 
these facts, the majority of typhoid fever epidemics are traceable to water 
infection, but indicate fresh contamination and not one of long standing. 

Within the human body the typhoid bacilli are found mainly in the 
intestine, also in the urinary bladder, and in the majority of cases in the 
blood stream. The bacilli are discharged from the body with the feces 
and the urine ; and are often present in such discharges for a period of 
ten weeks, and in chronic carriers for years after recovery. An added 

1 Nuttall, G. H. F., and Jepson, F. P., 1909. The part played by Musca 
domestica and allied (non-biting) flies in the spread of infective diseases. Re- 
ports to the local Government Board of Public Health and Medical Subjects. 
(New Series No. 16.) London. 

2 Jordan, Edwin O., 1908. A Textbook of General Bacteriology. W. B. 
Saunders & Co. Philadelphia, pp. 557. 



178 MEDICAL AND VETERINARY ENTOMOLOGY 

source of danger is the presence of virulent bacilli in very light cases 
of typhoid fever, known as " walking typhoid," where little or no pre- 
caution is exercised. 

The above facts aid in interpreting the role of flies in typhoid trans- 
mission. Flies are attracted by excrementous matter, as has already 
been stated, and thus contaminate their mouth parts and feet, which, 
if the feces contain virulent bacilli, must now fairly reek with filth and 
disease. Thus equipped the fly next makes its way to the dining 
room, grocery store, fruit stand, etc., depositing there on the human 
food the infective dejecta by means of its soiled proboscis and feet. 
Thus, during the Spanish American war, flies with lime-covered feet 
were actually seen crawling over the food of the soldiers. The whit- 
ened feet were the result of lime and filth collected from the camp 
latrines. The depredations of typhoid fever at that time really mark 
the beginning of the widespread campaign against the house fly. 

Jordan 1 states " not only may bacilli stick to the legs and wings 
of these insects, but if swallowed they may survive the passage of the 
alimentary tract. Typhoid bacilli have been isolated from house flies 
captured in houses in Chicago, in the neighborhood of badly kept privy 
vaults used by typhoid patients, and it has been shown experimentally 
that living bacilli may remain in or upon the body of flies for as long as 
twenty-three days after infection." 

The writer's attention was at one time called to a series of sporadic 
cases of typhoid fever, plausibly traceable to flies, thus : a certain car- 
penter recently recovered from typhoid fever, resumed his work, making 
use of a box privy, such as is often used in connection with buildings 
under construction. In the immediate vicinity there lived a milk dealer, 
who, after washing his cans, placed them on the roof of a shed to drain. 
Flies are fond of milk, even highly diluted with water. The cases of 
typhoid fever in question were, on investigation, found to be cus- 
tomers of this particular dealer. The argument is good and reasonably 
conclusive. 

The pollution of the waters of New York harbor has been made the 
subject of special study by Jackson. 2 In his report to the "Merchants' 
Association " of New York he shows that the sewage is not carried away 
by the tides, and " that at many points sewer outfalls have not been 
carried below the low-water mark, in consequence of which the solid 
matter from the sewers has been exposed on the shores." These deposits 
were found to be covered with flies, thus affording ample opportunity 
for the transmission of typhoid. It was, furthermore, found that the 
greater number of typhoid cases were found near the water front, and if 

1 Jordan, Edwin 0., 1908 (loc. cit.). 

2 Jackson, Daniel D., 1908. Pollution of New York harbor as a menace 
to health by the dissemination" of intestinal diseases through the agency of the 
common house fly. Report to the Water Pollution Committee of New York 
City. 



THE COMMON HOUSE FLY 179 

the curve showing the prevalence of cases was set back to accord with 
the average time of infection, it coincided with the curve showing the 
prevalence of house flies. The fly curve, of course, also coincides with 
the temperature curve, but hot weather cannot account for the dis- 
semination of the typhoid bacillus, nor for its presence. 

Various authors at sundry times have shown experimentally that 
Musca domestica can carry Bacillus typhosus after having fed on con- 
taminated material, both by contact with feet, proboscis and wings 
(Firth and Horrocks) 1 and via the digestive tract (Faichnie). 

Flies captured in houses occupied by typhoid fever cases have also 
been shown to be infected ; thus Hamilton found B. typhosus in five 
out of eighteen flies captured under the above condition in Chicago, 
and Ficker 2 made observations in Leipzig with similar results. 

Thus the case against the house fly as a carrier of typhoid is conclu- 
sive. 

Dysentery. — There are at least two varieties of dysentery ; of which 
one is caused by a bacillar organism, as in typhoid fever, and is known 
as Bacillus dysenteric, and the other variety is caused by a protozoan 
organism (Entamoeba) known as Entamasba histolytica. The former 
variety is known to be the prevalent type in temperate climates, while 
the latter is common in the tropics. The causative organism of both 
is found in great numbers in the stools of patients. The mode of 
infection is much the same as in typhoid fever. 

Summer Diarrhea in Infants. — A type of Bacillus dysenteric is 
present in the stools of infants suffering from summer complaint. 
Thousands of infants die every summer from this disease. Howard 3 
states that in 1908 the number of deaths due to summer complaint was 
52,213, of which 44,521 were under two years. It is thus in the helpless 
months of the child's life that this disease is most dangerous. At this 
age the infants are greatly molested by flies (when these are present) 
attracted by milk vomits and especially stools, which often remain 
exposed for a long time and to which flies have free access. From 
these stools the flies travel to the child's face and mouth where they 
linger menacingly. Mothers who fail to protect their babies against 
the disease-bearing house fly are criminally exposing these innocents to 
deadly disease. Keep the baby well protected by screens, and if by 
accident a fly has fallen into the milk, it is better to throw it away. 
Furthermore, milk receptacles can easily be kept covered, and the fly in 
the milk is usually a sign of carelessness. Carefully protect nipples and 
nursing bottles against flies. 

1 See Nuttall, G. H. F., and Jepson, F. P., 1909. The part played by 
Musca domestica and allied (non-biting) flies in the spread of infective diseases. 
Reports to the Local Government Board on Public Health and Medical Sub- 
jects. New Series 16, No. 4, pp. 13-41. 

2 Nuttall and Jepson, 1909 (loc. cit). 

3 Howard, L. O., 1911. The house fly, disease carrier. F. A. Stokes Co. 
New York, pp. xix + 312. 



180 MEDICAL AND VETERINARY ENTOMOLOGY 

Xuttall in summing up the evidence against the house fly makes the 
following statement, " All authorities agree that flies rest under strong 
suspicion of serving as disseminators of diarrheal infection." 

Tuberculosis. — Tuberculosis is caused by a specific organism, 
Bacillus tuberculosis, which may invade practically every organ and 
tissue of the human body. The lungs are commonly the seat of lesions, 
as are the intestines, the liver and the urogenital organs. The causa- 
tive germs find their way outside the body in the sputum, the feces 
and the urine, depending on the location of the lesions. 

In the study of transmission the considerable power of resistance 
which these bacilli possess is highly important. Dried phthisical 
sputum has been found to contain virulent bacilli after two months. 
Sputum has been found to contain living tubercle bacilli even after 
being allowed to putrefy for several weeks. The germicidal power 
of sunlight is very great, but according to Jordan 1 it requires from 
twenty to twenty-four hours' exposure to sunlight or even longer to 
kill the tubercle bacillus when present in sputum. 

These facts are most important when, coupled with them, it is rec- 
ognized that infection is commonly accomplished by way of the in- 
testinal tract, with infected food introduced into the mouth. " Von 
Behring maintains that the vast majority of all cases of lung tuber- 
culosis are of intestinal origin, and there is no doubt that pulmonary 
tuberculosis can originate from swallowing tubercle bacilli " (Jordan). 

It has been proved beyond doubt that the house fly can carry with 
it in its intestinal tract the Bacillus tuberculosis. " The belief that 
flies (Musca domestica) which have fed on tubercular sputum may 
serve as carriers and disseminators of the tubercle bacillus first led 
Spillmann and Haushalter (1887) to investigate the problem. They 
examined such flies and also their excreta deposited on the walls and 
windows of a hospital ward, and were able to determine microscopically 
the presence of large numbers of tubercle bacilli, both in the intestines 
of the flies and their excrement " (Nuttall). Howard quotes the follow- 
ing from a " paper by Dr. Frederick T. Lord (1904) of Boston " : 

" 1 . Flies may ingest tubercular sputum and excrete tubercle bacilli, the virulence 
of which may last for at least fifteen days. 

" 2. The danger of human infection from tubercular flyspecks is by the injection 
of the specks on the food. Spontaneous liberation of tubercle bacilli 
from flyspecks is unlikely. If mechanically disturbed, infection of the 
surrounding air may occur. 
"As a corollary to these conclusions it is suggested that — ■ 

" 3. Tubercular material (sputum, pus from discharging sinuses, fecal matter 
from patients with intestinal tuberculosis, etc.) should be carefully pro- 
tected from flies, lest they act as disseminators of the tubercle bacilli. 

"4. During the fly season greater attention should be paid to the screening of 
rooms and hospital wards containing patients with tuberculosis, and 
laboratories where tubercular material is examined. 

1 Jordan, Edwin 0., 1908 iloc. tit.). 



THE COMMON HOUSE FLY 181 

" 5. As these precautions would not eliminate fly infection by patients at large, 
foodstuffs should be protected from the flies which may already have in- 
gested tubercular material." 

The investigations by Dr. Ch. Andre of the University of Lyons were 
reported at the Anti-Tuberculosis Congress at Washington, 1908, viz. : 

"Flies are active agents in the dissemination of Koch's bacillus because they 
are constantly going back and forth between contagious sputa and feces, and 
foodstuffs, especially meat, fruit, milk, etc., which they pollute by contact with 
their feet, and especially with their excretions. 

" The experimental researches of the author show the following: 

" 1. Flies caught in the open air do not contain any acid-fast bacilli that could 
be mistaken for the bacillus of Koch. 

"2. Flies that have been fed on sputum evacuate considerable quantities of 
bacilli in their excretions. The bacilli appear six hours after ingestion of the 
sputum, and some may be found as long as five days later. These flies, there- 
fore, have plenty of time to carry these bacilli to a great distance, and to con- 
taminate food in houses apparently protected from contagion, because not in- 
habited by a consumptive. 

"3. Food polluted by flies that have fed on sputa contains infective bacilli 
and produces tuberculosis in the guinea pigs. 

"4. Flies readily absorb bacilli contained in dry dust. 

"5. Flies caught at random in a hospital ward produced tuberculosis in the 
guinea pig. 

"Practical conclusions. — The sputa and feces of tuberculosis subjects must 
be disinfected ; flies should be destroyed as completely as possible ; foodstuffs 
should be protected by means of covers made of wire gauze." 

Asiatic Cholera. — Asiatic cholera, as the name implies, is endemic 
in Asia (India), but has spread over the larger part of the world during 
the past century, becoming endemic in Africa and Europe. The 
disease relates to the intestinal tract, and is of bacterial origin (Spirillum 
cholero?). The cholera spirillum leaves the body with the stools, and 
infection is traceable to this source. " Upon the surface of vegetables 
and fruits kept in a cool moist place, experiments have shown that the 
spirillum may retain its vitality for from four to seven days " (Jordan). 

Cholera was among the first diseases with which the house fly was 
associated as a carrier, and the experimental evidence is truly convincing. 
Tizzoni and Cattini in Bologna in 1886 isolated cholera vibrios from 
flies caught in cholera wards. Simmonds in 1892 captured flies in the 
post-mortem morgue in Hamburg and isolated cholera vibrios from these 
in large numbers. 

There remains no doubt that flies are important carriers of cholera, 
and that bodies dead of cholera, stools and vomits of patients, should 
be protected from flies, and that foods should be most carefully screened. 

Frambcesia (tropical ulcer or yaws) is caused by Spirochceta 
pertenuis. The disease is widely distributed in the tropics. The 
spirochetes are found in the superficial ulcers on the hands, face, feet 
and other parts of the body. The following quotation from Nuttall 



182 MEDICAL AND VETERINARY ENTOMOLOGY 

and Jepson * is convincing enough that Musca domestica is amply 
able to transmit this disease : " Castellani (1907) tested the matter 
of the fly transmission of yaws by experimental methods. He allowed 
M. domestica to feed (1) upon yaws material (scraping from slightly 
ulcerated papules), and (2) upon semiulcerated papules on the skin of 
these yaws patients. In both cases he was able to discover the Spirochceta 
pertenuis in microscopic preparations made from the flies' mouth parts 
and legs. Furthermore, he allowed M. domestica to feed on yaws mate- 
rial (1 and 2 as above) and afterwards transferred them to scarified areas 
upon the eyebrows of monkeys. Of 15 monkeys thus experimented 
upon three developed yaws papules at the places which had been con- 
taminated by the flies." 

Ophthalmia. — In commenting on ophthalmia as carried by flies 
Howard 2 has the following to say : " Dr. Lucien Howe of Buffalo 
informed the writer (Howard) that in his opinion the ophthalmia of the 
Egyptians is also transferred by flies and presumably by the house fly, 
and referred the writer (Howard) to a paper which he read before the 
Seventh International Congress of Ophthalmology at Wiesbaden in 1888. 
He referred to the extraordinary prevalence of purulent ophthalmia 
among the natives up and down the river Nile and to the extraordinary 
abundance of the flies in that country. He spoke of the dirty habits 
of the natives and their remarkable indifference to the visits of flies, 
not only children, but adults, allowing flies to settle in swarms about 
their eyes, sucking the secretions, and never making any attempt to 
drive them away. Doctor Howe called attention to the fact that 
the number of cases of this eye disease always increases when the flies 
are present in the greatest numbers and the eye trouble is most prev- 
alent in the place where the flies are most numerous. In the desert, 
where flies are absent, eyes as a rule are unaffected. He made an ex- 
amination of the flies captured upon diseased eyes and found on their 
feet bacteria which were similar to those found in the conjunctival 
secretions. Flies captured in Egypt swarming about the eyes of 
ophthalmia patients and sent to Washington, D.C., were identified as 
Musca domestica." 

Other Diseases Carried by the House Fly. — Under certain favorable 
conditions it is also quite probable that the fly may be a carrier of 
anthrax, plague, gonorrheal infection, and possibly smallpox. 

Eggs of Parasitic Worms. — The most extensive and careful work 
on the dispersal of eggs of parasitic worms by the house fly has been 
done by Nicoll 3 and the following is a summary of his investigations 
in that respect. Flies feed readily upon infective material such as 

1 Nuttall and Jepson, 1909 (loc. cit.). 

2 Howard, L. O., 1911 (loc. cit.). 

3 Nicoll, William (1911). "On the part played by Flies in the Dispersal 
of the Eggs of Parasitic Worms." Reports to the Local Government Board on 
Public Health and Medical Subjects (New Series, No. 53). Further Reports 
(No. 4) on Flies as Carriers of Infection. London. 



THE COMMON HOUSE FLY 183 

excrement laden with eggs from parasitic worms and even upon evac- 
uated worms. Eggs may be conveyed by flies from excrement to food 
in two ways, namely on the external surface of their body and in their 
intestines. The latter mode is practicable only when the diameter of 
the eggs is under .05 mm. Eggs with a diameter of up to .09 mm. may 
be conveyed on the external surface; however, these adhering eggs are 
usually gotten rid of by the fly within a short time, while those harbored 
in the intestine may remain there for two days or longer. 

The eggs may remain alive and subsequently cause infection in 
either of these ways ; however, this depends on their resisting powers. 
It was found that material containing eggs of parasites, and in particular 
ripe segments of tapeworms, remain a source of infection through flies 
as long as two weeks. 

The eggs of the following parasitic worms were shown experimen- 
tally to be capable of transmission by Musca domestica: Tcenia 
solium, Tcenia serrata, Taenia marginata, Hymenolepis nana, Dipy- 
lidium caninum, Dibothriocephalus lotus (?), Oxyuris vermicularis, Tri- 
churis (Trichocephalus) trichiurus, both internally and externally, 
Necator americanus, Ankylostoma caninum, Sclerostomum equinum, 
Ascaris megalocephala, Toxascaris limbata (Ascaris canis e. p.), 
Hymenolepis diminuta externally only. No trematode parasites 
were experimented with and the observations of Stiles that the larval 
fly can ingest Ascarid eggs and pass them on to the adult fly was not 
confirmed. 



CHAPTER XIV 
HOUSE FLY CONTROL 

Introduction. — Agitation for the extirpation of any given species 
always brings with it a wave of protest based mainly on the idea that 
there is a balance in nature which should not be disturbed. The wise 
agitator calls for control rather than elimination, not merely to appease 
the wrath of opponents, but because control is possible, while elimination 
of any given species is practically impossible except for some species in 
given isolated regions. A cosmopolitan species of such abundance and 
extensive breeding habits as Musca domestica is an object for control 
rather than one for elimination. 

The house fly is regarded by many as necessary in Nature's economy, 
that it is most abundant where most needed. It is time and again 
asserted that the house fly, though admittedly a disease carrier, must 
be good for something, otherwise it would not be in existence, and 
should therefore not be molested. The following is an extract from a 
letter received by the writer, which illustrates well the objections fre- 
quently raised: 

"Dear Sir: I enclose a slip that I cut from a paper saying that you are 
down on the poor flies. Now, I would like to take their part. I have known 
them nigh on to thirty years, and I never knew of a sickness that could be laid 
to them. I know they make a lot of dirt, spoil picture frames and such, tickle 
your nose in the morning if you don't get up, but they make a nice food for 
young poultry. . . . Only a few years back they were considered a blessing, 
as they eat stuff that would make harm . . . they spot things, make a lot of 
cleaning, that keeps folks out of mischief. If mosquitoes or flies harm anyone, 
it's because the blood is out of order, and they had better look to it and mend 
their ways. ... I think if you would get after them of your size, such as . . . 
and . . ., they are parasites that do more harm than insects and reptiles com- 
bined ... so if you want to scrap go after them . . . this torturing poor 
helpless creatures to find ways to prolong lives that are worthless ... we 
must all die some way . . . hoping you will let the flies and little things 
alone. . . ." 

In reply to the above rather trivial objections it may be said in the 
first place that the house fly is by no means a good scavenger ; on the 
contrary its function in that regard is very poor, since the material in 
which it breeds is not greatly reduced, and secondly there is no good 
excuse for the collection and prolonged exposure of fecal material and 
decaying kitchen refuse in which the fly breeds. Simply on the basis 

184 



HOUSE FLY CONTROL 185 

of human decency such refuse should not be permitted to collect and 
remain exposed long enough to breed flies. Domesticated animals are 
necessary to our present state of civilization, but our methods of stable 
sanitation and manure disposal are far behind the times, all but 
barbaric. 

As innocent as flies may appear, they rank nevertheless among the 
most dangerous enemies of man. There is no virtue in the house fly, 
and there is no reason why it should continue to swarm in hordes in 
any civilized community. It is a poor advertisement for civilization. 
Dr. E. P. Felt 1 has so well said " our descendants of another century 
will stand in amazement at our blind tolerance of such a menace to 
life and happiness." 

The house fly can be controlled without question. This is demon- 
strated by the scarcity of flies in localities where cleanliness about 
stables and houses prevails throughout a number of adjacent city blocks. 
The work of control can be greatly furthered by the individual citizen, 
but as is so well stated by the California State Board of Health in Bulletin 
No. 11 (1909), " This work can be done only by a united effort. The 
citizen must do the work, and should do it willingly, but, if negligent, 
the strong hand of the law should compel it." The citizen must, how- 
ever, have instruction in the matter, because there is the greatest ig- 
norance relative to the life history and development of the housefly 
and disease-transmitting insects in general. The writer finds that this 
ignorance is as prevalent among the educated as among the uneducated. 

The main facts pertaining to development and habits indicate the 
most desirable control measures to be pursued. If 95 per cent of our 
house flies develop in horse manure, — and this is true under ordinary 
conditions, — the point of attack is clearly outlined. 

Sanitary Stable Construction. — Since the principal breeding places 
of the house fly are found in and about stables, particular attention 
must be paid such situations with special reference to the disposal of 
manures and urine. In the first place the stable should have a concrete 
floor. A very practical consideration of this subject is to be found in 
Bulletin No. 97, North Dakota Agricultural Experiment Station, from 
which the following suggestions are largely taken. Although higher 
than wood in first cost, cement concrete meets the requirements of a 
good floor better than any other available material. Concrete floors, 
according to the bulletin mentioned, are considered best for several 
reasons. "1. They are economical because they are durable. Wooden 
floors last from three to five years with a maximum of about ten years, 
if of the best construction, while the durability of good concrete floors 
equals that of the building. 2. They save labor because of their even- 
ness, which permits of thorough and easy cleaning. 3. They are sani- 
tary not only because they can be kept clean, but because they are 

1 Felt, E. P., 1909. Control of household insects. N. Y. State Museum 
Bull. No. 129, pp. 5^7. 



186 MEDICAL AND VETERINARY ENTOMOLOGY 

easily drained and are water-tight enough to exclude ground water and 
prevent the liquid manure from leaching into and polluting the soil. 

" The chief objection to concrete floors are that they are cold and 
slippery. To the first may be replied that in reality concrete is no 
colder than wood subjected to the same temperature but on account of 
being a better conductor of heat concrete carries away the bodily heat 
of the animals faster if they come in direct contact with it. This is not a 
serious objection, for even wood is too cold for animals to lie on without 
bedding, which should be supplied liberally on any floor. Straw is a 
poor conductor of heat and if a sufficient amount of bedding is used, the 
bodily heat of the animals will be retained as well on concrete as on wood, 
which is apt to be more or less wet or soggy. A generous use of bedding 
is desirable not only because it adds to the comfort of the animals, but 
because of the increased amount of manure which in turn means in- 
creased fertility of the farm. The objection of slipperiness may be 
overcome by making the wearing surface scored or grooved into blocks 
before it has hardened. These sections made from 4 to 6 inches square 
furnish a good foothold for the animals and make a very neat appear- 
ance. 

" The floor should be raised about one foot above the surface of the 
ground to insure drainage. If earth has been filled in to secure this 
elevation, it must be thoroughly compacted so as to prevent uneven 
settling and subsequent cracking of the floor. It is a good practice 
to make the desired fill as soon as the foundation is completed because 
it can be done more conveniently at that time and the fill will have 
proper time to settle before the floor is put on. 

" Concrete stable floors should be about 5 inches thick. The lower 
4 inches should be made of concrete in the proportion of one part cement, 
2| parts clean, coarse sand and five parts screened gravel or broken stone 
and finished before the concrete has set, with a one-inch mortar of one 
part Portland cement to two parts clean and coarse, but sharp sand. 
If the sand or cement are not first-class, this proportion had best be 
changed, for horse barns at least, to one part cement to 1 J parts sand. 

" Before laying the concrete a foundation of porous material, such as 
cinders or gravel, should be spread evenly on the surface and thoroughly 
tamped down. The depth of this foundation will depend upon the 
drainage of the soil but where a fill of one foot of earth has been pro- 
vided, as previously described, this foundation need not be more than 
four inches thick." 

In constructing a concrete floor provision must be made to carry 
away the urine from the animals and water used in cleansing the floors 
and stalls. Suggestions from the above-named bulletin are here again 
useful, namely, the stall floors should be given a 1 inch drop from the 
manger to the manure gutter, which latter should be " 6 inches deep 
and 14 inches wide. In order to facilitate the draining away of the 
liquids a 3-inch U-shaped channel is sometimes made in the bottom 



HOUSE FLY CONTROL 187 

of the gutter next to the manure alley, but this is not necessary where a 
slope is given the gutter bottom. The gutter should be given a uniform 
fall of 3 inches to 100 feet and the floor of the manure alley should have 
a slope towards the gutter of 1 inch to 10 feet. A small water-tight 
liquid manure cistern may be provided outside the barn into which the 
gutter drains, but if a manure shed is used the cistern should be in the 
shed. The gutter should be connected to the cistern by means of a 
drain pipe effectively trapped like the soil pipe in a house and so arranged 
that the trap may be easily cleaned. " In cities with sewer facilities 
connection is made directly with the sewer, dispensing with the manure 
cistern. 

Often the concrete stall floors are covered with wood so that the 
animals do not come in direct contact with the concrete. If such super- 
floors are provided, they should be made of heavy two-inch strips three 
inches wide and as long as the stall. The strips are fastened together by 
crosspieces (ordinarily flat iron strips) so that a space of about one half 
inch remains between the strips. To facilitate ease of handling it is 
strongly recommended that the floor be made in two long pieces, each 
half the width of the stall, and fitting closely where they join. In this 
way the superfloor can be lifted up while the concrete is being cleaned ; 
the crevices between the wood strips can be readily freed from manure 
by means of a heavy stream of water or iron rod. If the crevices are 
not also frequently cleaned, fly larvae will develop there very readily. 

Manure and odors of manure will attract the female flies even though 
the stable is somewhat dark. The writer believes that the small extra 
cost of screening a stable against flies is a good investment since it not 
only lessens the opportunity for flies to breed but also adds to the com- 
fort of the animals. 

Disposal of Manures. — Wherever horse manure is piled up in the 
open the opportunity is given for flies to breed. In the preceding chap- 
ter it was pointed out that an average manure pile weighing about 
half a ton, after an exposure of only four days harbored approximately 
450,000 fly larvae. As before stated it requires only about four days 
for the larvae to reach full growth, after which they begin to migrate into 
the drier portions of the heap and crawl out into near-by debris, beneath 
platforms, etc. It is therefore imperative, if fly breeding is to be pre- 
vented, that manure be protected against flies from the beginning, or 
that it be rendered undesirable to flies, or that it be otherwise disposed 
of. 

Under ordinary rural conditions the most practical method is to 
remove the manure to the field daily. A cart may be used for this 
purpose ; it is daily backed up against the stable doorway, the manure 
thrown in and carted away at once to a field where it is scattered. This 
saves much time in handling and is sound agricultural practice. Since 
moisture and warmth are both necessary for the development of fly 
larvae the scattered manure cannot serve this purpose. 



188 MEDICAL AND VETERINARY ENTOMOLOGY 

If more desirable, the manure may be placed in deep narrow trenches 
(preferably concrete) each day and daily covered with slaked lime and 
earth and allowed to rot. The disadvantage is that the manure must 
be dug up from the trenches later when it is to be used as fertilizer. 
However, the former method is more practical and is highly recom- 
mended. The Wisconsin Bulletin No. 221 states : " Manure is never so 
valuable as when perfectly fresh, for it is impossible under the best 
system of management to prevent all loss of its fertilizing ingredients. 
For this reason, whenever possible, the manure should be hauled directly 
to the field and spread. The system saves time and labor as it in- 
volves handling but once. The manure will be leached by the rain and 
snow, nevertheless the soluble portion will be carried into the soil, where 




Fig. 127. — Manure bin in a position to become a fly breeding cage, instead of a fly pre- 
ventative. It is suggested that the lid be permanently closed, and an opening made 
directly from the stable into the bin. The manure pile adjoining the bin illustrates 
the manner of disposal before the bin was built. 



it is needed. When spread in a thin layer, it will not heat, so there 
will be no loss from hot fermentation, and where manure simply dries 
out when spread on the ground there is no loss of valuable constituents." 
The question is raised, — will not chickens eat the maggots and thus 
keep in check the flies in manure piled up in the barnyard ? It must be 
considered that manure piled up sufficiently deep to permit fly larvae 
to develop in it does not permit chickens to scratch their way through 
the heap and consequently they can only destroy a small fraction of the 
larvae ; and where the manure pile is low enough for chickens to scratch 
it over and over, the fly larvae would not develop anyway owing to the 
dryness and lack of heat. Furthermore, it is not safe to permit chickens 
to feed on maggots owing to the fact that the larva of a common and 



HOUSE FLY CONTROL 



189 



dangerous poultry tapeworm is commonly harbored by these insects. 
Farmers and gardeners who wish to use "rotted" manure for fertilizing 
purposes should screen the heap until the " rotting " process is well 
under way, when fly breeding will be reduced to a minimum, or, as has 
already been suggested, the manure may be placed in trenches and 
covered with lime and earth whenever fresh manure is added or it 
may be stored in fly-tight composting pits. 

Manure Bins. — Under city conditions it is ordinarily impracti- 
cable to remove manure from the premises daily, hence it must be 




Fig. 128. — A properly constructed manure bin with opening directly from stable into bin. 
May or may not be elevated on legs to facilitate removal of manure to wagon. Size of 
bin depends on number of horses and frequency of manure removal. 



stored temporarily in special receptacles or bins. Heretofore stress 
has been laid on fly-tight receptacles, but unless exceptional care is 
exercised in operating such receptacles, they actually become fly-breed- 
ing cages. The writer early recognized this difficulty and suggested 
a remedy as below described. 

Fig. 127 illustrates a manure bin of the earlier type. The manure 
pile near by illustrates the manner of disposal before the bin was erected. 
In this case the lid of the bin must be kept open while the manure is 
being transferred to it from the stable, and during this time flies enter 
the box in numbers, and when the lid is closed they are trapped, 
deposit their eggs and soon the manure is reeking with maggots and if 
the bin is not cleaned out before the expiration of nine or ten days 
myriads of flies emerge and are liberated when the lid is opened. 



190 MEDICAL AND VETERINARY ENTOMOLOGY 



1\ cubic feet of manure per day, including 



The bin is built on a concrete floor to prevent rats from nesting 
underneath, it is painted with creosote inside and ventilation is pro- 
vided for at both ends by means of screened openings. The screen 
should be of copper wire to prevent rapid rusting. The front of the 
bin is provided with a hinged door which lifts up so that the manure 
can easily be removed. The dimensions are approximately as follows : 
length, 8 ft. ; width, 4 ft. ; height in front, 4 ft. ; height in back, 5 ft. 
The size of the bin, or composting pit if this is used, depends, of 
course, on the number of horses stabled and length of time during 
which the manure remains in storage. It may be estimated that the 
average horse produces 
bedding. 

To prevent the bin from becoming a fly-breeding cage, the writer 
recommends that the top be permanently closed, i.e. without a lid, 
and that the manure be thrown into the bin directly from the stable 
through a small door cut through the side of the stable into the bin near 
the top of the same (Fig. 128). This opening can easily be provided 
with a small sliding, screened door. Furthermore the bin should be 
built so that the small door last mentioned can 
be located in a dark part of the stable, thus 
further preventing flies from entering the bin. 
At a small added cost fly traps can be attached 
at the ventilator ends of the bin in such a man- 
ner that chance flies in the box will enter these 
and be entrapped. Because the flies respond to 
the light they will naturally gather at the ven- 
tilator ends and if the traps are baited with some 
material attractive to the flies, there is an added 
inducement to enter. 

Garbage Cans. — The writer has been favor- 
ably impressed with the type of combined gar- 
bage can and fly trap invented by Professor C. F. 
Hodge. By his permission a diagram is here 
given (Fig. 129), together with his explanation of 
the same (see Nature and Culture, July, 1911), viz. : " The principle of 
operation is that hungry flies will crawl in toward the smell of food 
through any dark crack and, after feeding, will fly out toward the light. 
They enter the garbage can or other receptacle by smell, and attempt 
to leave by sight. It is necessary to have the cover about half an 
inch larger in diameter. Three pieces of sheet iron are soldered inside 
the rim, equidistant apart to hold it up a crack, and keep it spaced 
out from the rim of the can about one fourth of an inch all around. 
In a swill barrel, nails may be driven into the rim and bent over to 
hold the cover properly, but direct light must not enter this crack. Cut 
a hole in the cover at least three inches in diameter and fasten the 
trap over this opening according to plain directions sent out with each 




Fig. 129. — An effective 
combination garbage can 
and fly trap. (After 
Hodge.) 



HOUSE FLY CONTROL 



191 



trap. With everything in the way of waste food material put into this 
receptacle, you establish a ' focus/ a ' vacuum cleaner ' for flies, and 
properly managed, this will prove exterminative." 

Where ordinary garbage cans are used and certainly every household 
should possess a garbage receptacle that can be tightly closed against 
flies (unless above plan is followed), it is strongly urged that all liquids 
be drained from the refuse before disposing of it and that the solids 
be wrapped in a newspaper before placing in the can. In this way fly 
breeding in garbage cans may be effectually prevented and an act of 
mercy is done the scavenger and others as well. 

Garbage Collection and Disposal. — Not only must the garbage can 
and its proper use be insisted upon in this connection, but also the 
proper collection of the garbage by the scavenger. Few sights are 
more disgusting than that of an open garbage wagon reeking with its 
load of vile-smelling offal and swarming with flies. During the straw- 
berry season it is a matter of dailv occurrence in manv cities to see 




Fig. 130. — Flies are commonly and abundantly distributed through the community by 
poorly arranged garbage wagons. Properly constructed, closed, city-owned and regu- 
lated garbage wagons must take the place of the above pernicious system. 



the garbage wagon (Fig. 130) traveling side by side with the strawberry 
wagon, flies crossing from one to the other without restriction. This 
is certainly revolting if not also a menace to health. Municipal col- 
lection of garbage in properly constructed city-owned garbage wagons 
is the only solution of the present outrageous common system. 

No more sanitary way of disposing of garbage can be devised than 
that of incineration. The garbage dump will always be a fly producer, 
particularly if it receives manures and moist offal. 



192 



MEDICAL AND VETERINARY ENTOMOLOGY 



The Sanitary Privy. — The house fly breeds in enormous numbers in 
human excrement if given the opportunity, particularly in open, shallow 
privies. Not only are the newly emerging flies laden with filth, but also 
flies from the whole neighborhood which have congregated about such 
filth places, going back and forth between these and the family kitchen 
and dining room. This outrage against civilization calls for fly-proof 
privy construction. Many small communities have no sewer system, 
hence the use of the old-fashioned privy (Fig. 131) is still in vogue, 
though in many places there is now installed the septic tank system 
which permits of sanitary conveniences in the home at a reasonable 
cost. The septic tank places within the reach of all farm homes the 
establishment of modern sanitary conveniences in the house, free from 
any possibility of fly breeding. However, the appended figures of a 
sanitary privy suggested by the California State Board of Health 
Bulletin, Vol. 6, No. 6, after Stiles (Fig. 132), will furnish the 
reader with an adequate idea for the construction of a fly-tight 
privy. It must be borne in mind that simply covering the excreta 




Fig. 131. — Privy, swarming with flies, adjoining kitchen door. These conditions, invit- 
ing disease and insuring the pollution of food, are practically duplicated in hundreds 
of towns. (By courtesy of The Survey.) 



with dry earth does not prevent flies from breeding therein. In the 
absence of a fly-tight privy it is advisable to add quantities of chloride 
of lime, crude oil, or kerosene to the excreta two or three times a 
week. 

Fly Traps. — Unless fly traps are used to capture the flies as they 
emerge from their breeding place, as already described, such measures 
are ordinarily only excuses for the more important cleaning-up proc- 
ess ; the entrapped flies have ordinarily already had ample opportunity 
to carry filth and germs and deposit their eggs. However, traps may 



HOUSE FLY CONTROL 



193 



be useful adjuncts to other more permanent corrective measures, — 
the more flies captured the better, but the trapping should begin very 
early in the spring in order to capture the early flies which are responsible 
for the later multiplied millions of the same species. Many good fly 
traps are on the market and these may be baited with milk soaked 
bread, stale beer, or the juice of crabs. 

Insecticides on Manure Piles. — The writer is constantly requested 
to recommend insecticides that may be applied to manure in order to 
either destroy fly larvae or prevent fly breeding. He has for some time 
consistently refrained from making such recommendations, because, in 
the first place, such methods seem to be accepted as a substitute for 
cleaning up, and, in the second place, owing to the necessity for constant 
repetition, applications of the same would certainly be neglected. 
Furthermore the expense of the daily use of insecticides in efficient 
strengths is forbidding to the man of ordinary means. 

Ordinary applications of the usual insecticides prove of no avail. 
The cheapest, and at the same time the most effective, preparations must 
be applied two to five times as strong as when used against other insects, 





Fig. 132. — A sanitary privy, — front view to left ; rear and side view to right. (After 

Stiles and Lumsden.) 



and furthermore the larvae cannot be easily reached, buried as they 
are in the straw and manure. In the face of these conditions the 
more reliable and really simpler methods already mentioned are rec- 
ommended. 

Chemicals used to destroy the larvae may be roughly divided into 
two classes, viz. (1) contact poisons, and (2) stomach poisons. To the 



194 MEDICAL AND VETERINARY ENTOMOLOGY 

first class belong such preparations as kerosene, chloride of lime, etc. 
To the second class belong the arsenicals represented by arsenate of 
lead and paris green. 

Where the manure can be spread out to a depth of about half a foot 
it may be drenched with a distillate petroleum, which possesses a high 
flash point, i.e. does not ignite easily, and which has the necessary 
insecticidal value. Kerosene Emulsion should be applied at the 
rate of one part of the oil to five parts of water. If distillate oils 
of a loiv flash point are used about stables and outbuildings, the danger 
from fire must not be overlooked. The manure so treated cannot be used 
for fertilizing purposes. 

Chloride of lime, also a contact insecticide, applied liberally to the 
manure is effective, but, like the above, is expensive when used in 
proper quantities. 

TABLE XI 

Showing the Effect of Various Insecticides and other Materials on 
Fully Grown House Fly Larvae 

The larvae were placed in shell vials, two larvae in each, ten for each set. The 
vials were capped with filter paper and a strip of the same material soaked in 
tap water was placed inside with the larva?. Check sets treated with tap 
water were run in connection with each experiment. Temperature con- 
ditions were favorable in all cases. Whenever less than 90 per cent of the 
check larva? emerged as flies the entire experiment was discarded. Each 
material was given at least two tests, ordinarily by different persons. 



Name of Material 
Used 


COXCENTRATIOX 


KiiTe^ terial Used 


Concentration 


No. OF 

L-ARY.E 

Killed 


Carbolic acid . . . 


2\% 


100% Lime sulphur 


straight 


o 


Carbolic acid 




1% 


90% 


Pyroligneous acid 


straight 


o 


Creolin .... 




2f% 


100% 
100% 
100% 








Creolin 




5% 
10 % 


Boracic acid 


saturated solution 


100% 


Creolin . . . 






Kerosene . . _ . 




straight 


100% Boracic acid 


40% solution 


90% 


Kerosene emulsion 




1 to 10 


0%c Borax 


powder 


80% 


Kerosene emulsion 




1 to 8 


50% Formaldehvde 


4% 


100% 


Kerosene emulsion 




1 to 5 


100% Formaldehyde 


2% 





Nicotine sulphate 




40% 


80% Ferric sulphate 


saturated solution 


10% 


Nicotine sulphate 




20% 


80% 






Tobacco dust 




high grade 


Common salt 


saturated solution 





Ferrous sulphate 




saturated solution 


0-10% Sodium cyanide 


1% solution 


100% 


Ferrous sulphate 




10% 


Sodium cyanide 


A of 1% 





Ferrous sulphate 




20% 


Pvrethrum powder 


straight 


80% 


Potassium dichromate 


saturated solution 


100% Gypsum 


straight 





Potassium dichromate 


20% 


100% Carbolate of lime 


straight 


100% 


Potassium dichromate 


10% 


80% 






Potassium dichromate 


5% 


40% Carbolate of lime 


mixed with manure 


20% 


Potassium dichromate 


1% 


30% 






Chloronaphtholeum 


1 to 100 


100% Phenoco 


1 to 100 


20% 


Chloronaphtholeum 


1 to 200 


100% Phenoco 


1 to 200 


100% 


Chloronaphtholeum 


1 to 300 


30% 






Chloronaphtholeum 


1 to 400 


Pvxol 


1 to 200 


50% 


C.N 


1 to ]00 


100% Pyxol 


1 to 100 





C.N 


1 to 200 


100% Pyxol 


1 to 50 


90% 


C.N 


1 to 500 


70% i 







HOUSE FLY CONTROL 195 

The use of arsenical poisons has not been thoroughly tested by the 
writer ; indeed he hesitates to recommend these materials for general 
use because of the danger to domesticated animals in and near the 
barnyard; however, Newstead * states: "the application of paris green 
(poison) at the rate of two ounces to one gallon of water to either 
stable manure or ashpit refuse will destroy 99 per cent of the larvae. 
Possibly a smaller percentage of paris green might be employed with 
equally good results. One per cent of crude atoxyl in water kills 100 
per cent of fly larvae." The application of either of these substances 
might, however, lead to serious complications and it is very doubtful 
whether they could be employed with safety. 

In an experimental study of a large number of insecticides as applied 
to fly larvae, the writer, in cooperation with several of his students, has 
obtained the above results (see Table XI). 

The above table includes only a partial list of materials tested out 
in the laboratory, and indicates that there are a number of remedies 
heretofore advertised as efficient in the control of fly larvae, now proved 
to be without virtue, among them pyroligneous acid, gypsum, and 
iron sulphate. On the other hand there are quite a number of materials 
which have proved efficient, notably carbolic acid 1 per cent to 2\ per 
cent, creolin 2\ to 5 per cent, kerosene emulsion 1 to 5 per cent, potassium 
dichromate 20 per cent, sodium cyanide (very dangerous) 1 per cent 
solution, chloronaphtholeum 1 to 200, "C. X." 1 to 200, and boracic acid 
in saturated solution. The U. S. Department of Agriculture recom- 
mends applying .62 pound borax or .75 pound calcined colemanite to 
every eight bushels (10 cu. ft.) of manure immediately on its removal 
from the barn. The borax is to be applied by means of a flour sifter 
to the outer edges of the pile and sprinkled with two or three gallons 
of water. Hellebore is also recommended. 

In applying these materials and others already mentioned for the 
destruction of fly larvae, two things must be borne in mind, namely 
(1st) that the manure pile must be drenched in order that the chemical 
may reach the individual larvae, and (2d) what effect will the chemicdl 
have on the fertilizing value of the manure ? 

Hot Water Method. — It is, of course, well known that manure stored 
in tight vessels and covered well with water does not breed house flies. 
The writer has also carried on a number of experiments with hot water, 
particularly in such cases in which the manure is already inhabited by 
fly larvae and it is desired to use the same or remove it. Water heated 
to 90° C. (195° F.) and applied in saturating quantities destroys all 
larvae. At 85° C. and below all continue to develop. 

Two objections are commonly raised against this method of treat- 
ment : (1st) that the useful bacteria are destroyed, i.e. that the manure is 

1 Newstead, R., 1908. Life cycle and breeding places of the common 
house fly (Musca domestica Linn.). Annals of Tropical Medicine and Para- 
sitology, Vol. 1, No. 4, pp. 507-520. 



196 MEDICAL AND VETERINARY ENTOMOLOGY 

rendered sterile, and (2d) that all other desirable constituents are 
leached out by the water. These objections are not altogether well 
founded. Not all of the useful bacteria by any means are destroyed 
by the hot water and those remaining quickly multiply and soon render 
the manure as good as ever. In the second place the leachings may be 
preserved quite easily by first placing the manure in a tight shallow box 
similar to those used by plasterers for mixing mortar, and adding a 
spigot or simply boring a large hole in the bottom and inserting a plug, 
thus preserving the ingredients until allowed to flow out of the hole 
into a pail to be applied as liquid manure. 

The above-described method is particularly useful to gardeners and 
mushroom growers who must use rotted manure, in which fly larvae of 
many species occur very abundantly. 

The Fly in the House (Fly Poisons). — Because of the disease-trans- 
mitting powers of flies they should be kept away from human food. 
Fly swatters should be used vigorously and daily. Screens must con- 
tinue to be used until the community as a whole learns to apply the 
simple measures for the control of the fly, when screens will no longer 
be needed, and that time is not far off. The use of poisonous (arsenical 
and cobalt, etc.) preparations upon which the flies may feed is not 
recommended, inasmuch as the poisoned insects may drop into foods, 
a matter perhaps of small importance, but what is more important, many 
of these preparations are a menace to human life, especially to small 
children. The writer has found (as already suggested by others) that 
formaldehyde, properlv used, forms a very good substitute for arsenical 
or cobalt poisons. Various dilutions and combinations were tried, 
but a 2 per cent solution sweetened somewhat with sugar or honey (or 
even without sweetening) proved most desirable. Formaldehyde is 
inexpensive when thus used, and has the added advantage that it is 
relatively not poisonous to man in weak concentrations, and may, 
therefore, be used with little fear. It is also one of the most powerful 
germicides known, and is not injurious to delicate fabrics. Formaldehyde 
is ordinarily purchased in from 38 to 40 per cent solutions and should 
be diluted with water to about 2 per cent (add about twenty times as 
much water). The solution should be placed in shallow vessels on 
window sills, on the table or in the show window. It is not an easy 
matter to control the fly in a dining room where there are plenty of 
liquids for food and drink, such as water, milk, sweets, etc., hence, these 
should be removed or covered, for example, in the evening and the dishes 
of formaldehyde then put in place ; the flies will drink the poison the first 
thing in the morning and the end will be readily accomplished. One 
is thus taking advantage of the fact that the fly seeks something to 
drink early in the morning. Placing a piece of milk-soaked bread in 
the dish of formaldehyde adds somewhat to the efficiency. During the 
day the fly poison acts best when placed in a sunny spot. For outdoor 
work formaldehyde is equally efficient, but must be made inaccessible to 



HOUSE FLY CONTROL 197 

chickens, birds and other animals by screening with coarse-mesh 
wire. 

Various fumes created by burning one or the other of the following 
materials will stupefy the flies, — pyrethrum powder (Persian pyrethrum 
or Chrysanthemum cinerariafolium) , buhach, dried Jimson weed leaves 
(Datura stramonium) mixed with crystals of saltpeter (see under mos- 
quitoes), fumes of "cresyl," etc. The fly-fighting committee of the 
American Civic Association recommends the following : " Heat a 
shovel, or any similar article, and drop thereon 20 drops of carbolic 
acid ; the vapor kills the flies." 

Other Precautions. — It is highly important that sick rooms be 
well screened, especially in cases of certain transmissible diseases, 
such as typhoid fever, tuberculosis, etc. For the protection of the out- 
side world any flies that chance to find their way inside after the best 
precaution has been exercised should be killed to prevent their escape. 
Pus rags, bandages, sputum cloths, and the like, should not be carelessly 
thrown into the open garbage barrel where flies freely congregate. It 
may seem unnecessary to even mention these simple sanitary measures, 
but the writer has seen the grossest neglect in matters of this kind, even 
where better judgment should have prevailed. 

Natural Enemies. — The most important natural enemy of the 
house fly is the fly fungus, Empusa muscai, first described by DeGeer 
in 1872 (Howard) and rediscovered annually by enthusiastic human 
enemies of the house fly. During late summer and autumn and through- 
out the moist winter in California, dead flies are frequently found cling- 
ing to curtains and walls ; the abdomen is usually greatly distended, 
showing distinct bands due to the appearance of the intersegmental 
tissue brought to view by the pressing apart of the darker segmental 
rings. The disease is commonly kndwn as fly cholera. 

This fly fungus originates from spores which, when a fly is attacked, 
produce hyphse, thread-like processes which enter the body of the fly 
and develop a mesh work of threads, producing great distension of the 
fly's abdomen. This mycelium later evidently sends out hyphse through 
the intersegmental tissue, which hyphse then produce spores or conidia. 
The spores are then separated often with some force, and may produce 
a sort of " halo " about the now dead fly. Other flies thus become 
easily infected. The writer has lost experimental colonies of flies in 
great numbers in this way in less than two weeks after the appearance 
of the disease. 

Another very common parasite of the fly is a red mite, Acarus 
muscarum. Often three or four of these mites may be seen as tiny red 
specks on the head, neck or thorax of the house fly. Occasionally they 
actually retard the fly in its flight. 

When rearing house flies from pupae collected out of doors one is 
frequently surprised to find that 50 per cent or more give rise to a 
tiny dark metallic wasp which creeps out of the pupa case through a 




198 MEDICAL AND VETERINARY ENTOMOLOGY 

minute hole. These are chalcidoid wasps, one species of which is known 
as Nasonia brevicornis. 

While house flies are also attacked by various other natural enemies, 
such as spiders, robber flies, toads, lizards, etc., their generation does 
not seem to be greatly affected, and man must depend more and more 
on suppressing the breeding places of the pernicious pest or suffer the 
consequences. 

The Community Fly Crusade. — Under city or town conditions the 
crusade against the fly must be backed up by the intelligent interest 
of the citizens. Through intelligent cooperation it should be possible 
to reduce the fly population of any city or town by 95 per cent during 
the course of a single summer, and if action is taken in the autumn to 
eliminate breeding places and destroy overwintering flies, the following 
summer could be made practically flyless. 

Numerous crusades against the housefly have been conducted in 
many cities in the United States with good results. In each case the 
work has usually been begun by an organization, already in existence, 
such as a Women's Club, Civic Club, Chamber of Commerce and 
occasionally a Board of Health. Methods of procedure are usually 
outlined by competent Medical Entomologists, Parasitologists, Medical 
Officers or other individuals. 

To carry out the suggested permanent preventive measures, etc., 
a community should, to begin with, have an appointed staff of trained 
inspectors, the number varying with the size of the community ; four 
capable men working in pairs can cover considerable territory very well. 
No community should be without regular, trained sanitary inspectors 
under the direction of the Board of Health. The position of sanitary 
inspector should carry with it some dignity, and should be filled by men 
instructed in practical hygiene, including a fair knowledge of medical 
entomology, owing to the importance of insects in their relation to 
disease transmission. 

The best results will always be secured when the work is done through 
the Board of Health with as many civic organizations, schools, clubs, 
etc., as possible in intelligent and systematic cooperation to spread the 
propaganda. The active assistance of the school children may well 
be enlisted for the sake of the lesson in community service. However, 
little can be said in favor of offering prizes for a given quantity of flies. 
Let the children be taught where flies originate, their habits, etc., 
and then let the children report the presence of flies, say by counts, 
in certain situations, stores, homes, etc., and locate and report breeding 
places particularly. There will be just as much interest and enthusiasm, 
the ultimate results will be better and the opportunity to deal in flies is 
not a factor, — the children are dealing in terms of cleanliness, hygiene 
and sanitation. 

"Fly swatting" only serves to attract the attention away from the 
real issue, namely, the control of breeding places. However, a wise, 



HOUSE FLY CONTROL 



199 



properly guided agitation in this direction in the winter and spring would 
serve to reduce the early crop of flies materially, and the interest thus 
secured could gradually be won over to the side of civic cleanliness and 
the slogan will have 
changed from "swat 
the fly" to "swat the 
manure pile." 

Communities in 
which a campaign 
against the house fly 
has been undertaken 
with a determination 
to win have shown 
that this insect can 
be controlled, and 
this without great 
labor and expense. 
The problem is sim- 
pler than many are 
willing to admit. 
Hearty cooperation 
is essential. Every- 
body is concerned, 
and everybody will 
share in the victory 
and share in the sav- 
ing of financial and 
vital losses. Remem- 
ber this, — the pres- 
ence of many flies 
always denotes a dirty 
environment. 

Figure 133 illus- 
trates the type of 
literature used by va- 
rious communities in 
their crusade against 
the fly, and Fig. 134 
shows a part of the 
" House-fly Exhibit" at 
the Baby Saving Show 
held in Oakland, Cali- 
fornia, in 1914. 

Manure, Stable and Fly Ordinances. — Under ordinary conditions 
the crusade against the fly must also be a matter of ordinance backed by 
the intelligent interest of the citizens. One stable owner who does not 



J EEWARE of . 

, THE 
' .J DANGEROUS 
; I HOUSEFLY 

1 ^ 


, ^^^^^^^^^SI^JJ 


^^^* 








QUEjmEONS 

HOUSE 
STABLE FLY 


• ;>J ~-— . — 


~l-_ _: 


■V- ,^ — ^ , 


■ 


vJV^i- JBSK- 


Bf 






■ iHel^The 
£**! f Woman's 

m | ciub Fight 

j£ I The Flies 

1 


3 




H Remember 

AOrmCJty 








Ffiw carry unnmnable ^H 

filth lo food 1 counted ■ 

of butim. 








Here Is 
the Enemy 

for the 
Nation to 

Kijiht 

SPECAL BuU.6T,-« 

BEWARE g. m wmm HOUSE-F 


LY! 


■ L MUIFMHALM8 1 


HTH TNI FLY SJffilKC 


[; 1* tferiMS' hz^s 


|T- iVSM^JlV"" **• ,,C * j 

rJS c :iiiii L '-d-:?'^" -'■ 

L FLIES: * 


g* 1 ** "'^C 








1 \ 




: Si 


1 



Fig. 



133. — Literature, bulletins, etc., used by various com- 
munities in their crusades against the house fly. 



200 MEDICAL AND VETERINARY ENTOMOLOGY 




HOUSE FLY CONTROL 201 

believe in the " notion " that flies originate in horse manure (and there 
are not a few of that kind), can easily supply flies for several adjacent 
city blocks, hence there must be some ordinance to compel action. 

Ordinances must be practical so that it is possible to comply there- 
with, must be constitutional and must provide for a basis for conviction, 
i.e. our newer manure ordinances will point out that the presence of 
fly larvae or pupae is sufficient evidence that the provisions of the ordi- 
nance have not been complied with. 

Ordinances aimed at the fly nuisance fall under three heads, namely, 
(1) Stable ordinances, (2) Manure ordinances, (3) Food ordinances 
(protection against dust and flies). 

Stable Ordinances. — The following regulations, according to 
Howard, 1 are in force in the District of Columbia : 

" Sec. 18A. No person owning, occupying or having use of any stable, shed, 
pen, stall, or other place within any of the more densely populated parts of the 
District of Columbia, where animals of any kind are kept shall permit such stable, 
shed, pen, stall, or place to become or to remain filthy or unwholesome. 

"Sec. 1SB. No person shall use any stable, nor shall any person having the 
power and authority to prevent or permit any person to use any stable, within 
any of the more densely populated parts of the District of Columbia, after the 
first day of July, 1907, unless the surface of the ground beneath every stall and 
for a distance of four feet from the rear thereof be covered with a water-tight 
floor laid with such grades as will cause all fluids that fall upon it to flow as 
promptly as possible, if a public sewer be available, into the public sewer, and, 
if a public sewer be not available, to that portion of the premises where they will 
cause the least possible annoyance. 

"Sec. ISC. Every person owning or occupying any building or part of a 
building within any of the more densely populated parts of the District of 
Columbia, where one or more horses, mules, cows, or similar animals are kept, 
shall maintain in connection therewith a bin or pit for the reception of manure, 
and, pending the removal from the premises of the manure from the animal or 
animals aforesaid, shall place such manure in said bin or pit. The bin or pit 
required by this regulation shall be located at a point as remote as practicable 
from any dwelling, church, school or similar structure, owned or occupied by any 
person or persons in the neighborhood of said bin or pit, other than the owner or 
occupant of the building or part of building aforesaid and as remote as prac- 
ticable from any public street or avenue ; shall be so constructed as to exclude 
rain water, and shall in all other respects be water-tight except as it may be 
connected with the public sewer or as other definite provisions may be made for 
cleaning and flushing from time to time ; shall be provided with a suitable cover, 
and constructed so as to prevent in so far as may be practicable the ingress and 
egress of flies. No bin or pit shall be constructed the bottom of which is below 
the level of the surface of the surrounding earth unless it be of substantial 
masonry and connected with the public sewer. The provisions of this paragraph 
shall take effect from and after the expiration of three months immediately 
following its promulgation. 

il Sec. 1SD. No person owning or occupying any building or part of a build- 
ing located within any of the more densely populated parts of the District of 
Columbia in which building or part of a building any horse, mule, cow or similar 
animal is kept, shall keep any manure, or permit any manure to be kept, in or 
Upon any portion of the premises other than the bin or pit provided for that 

1 Howard, L. 0., 1911. The housefly, disease carrier. Frederick A. 
Stokes Co., New York, xix -f 312 pp. 



202 MEDICAL AND VETERINARY ENTOMOLOGY 

purpose ; nor shall any person aforesaid allow any such bin or pit to be over- 
filled or to be needlessly uncovered. 

"Sec. 1SE. The provisions of paragraphs C and D shall not apply to the 
keeping of manure from horses when such manure is kept tightly rammed into 
the well-covered barrels for the purpose of removal in such barrels. 

"Sec. 1SF. No person shall permit any manure to accumulate on premises 
under his control in such a manner or to such an extent as to give rise to objec- 
tionable odors upon any public highway or upon any premises owned or oc- 
cupied by any person other than the person owning or occupying the premises 
on which said manure is located. Every person having the use of any manure, 
in any of the more densely populated parts of the District of Columbia, shall 
cause all such manure to be removed from the premises at least twice every week 
between June first and October thirty-first, inclusive of each year, and at least 
once every week between November first of each year and May thirty-first 
of the following year, both dates inclusive. 

"Sec. 1SG. Every person using within the District of Columbia any build- 
ing, or an} r portion of a building, in the city of Washington, or in any of the more 
densely populated suburbs thereof, as a stable for one or more horses, mules or 
cows, shall report that fact to the health officer in writing, within thirty days 
after this regulation takes effect, giving his or her name, and the location of such 
stable, and the number and kind of the animals stabled therein ; and thereafter 
every person occupjdng any building, or any portion of a building, in the city of 
Washington, or in any of the more densely populated suburbs thereof, for the 
purpose aforesaid, shall report in like manner his or her name and the location of 
said stable, and the number and kind of animals stabled therein, within five 
days after the beginning of his or her occupancy of such buildings ; provided, 
that stables recorded at the Health Office as parts of dairy farms in the District 
of Columbia need not be so reported. 

"Sec. 1SH. No person who has removed manure from any bin or pit, or any 
other place where manure has been accumulated, shall deposit such manure in 
any place within any of the more densely populated parts of the District of 
Columbia without a permit from the health officer authorizing him so to do and 
then only in accordance with the terms of such permit. The provisions of this 
paragraph shall not apply to the distribution of manure over lawns and parking 
when such manure has been so thoroughly rotted or decomposed that its dis- 
tribution gives rise to no offensive odors on adjacent properties or on public 
thoroughfares." 

The stable ordinance in force in Berkeley, California, contains the 
following sections : — 

"Sec. 3. Where the premises on which any stable barn, shed or stall is 
maintained in which any horse, mule or cow is kept, fronts on a street in which is 
constructed a sewer the following requirements shall be complied with, viz. : 
The drainage from all single and box stalls where a horse, mule or cow is kept or 
housed, must in all cases be connected to the street sewer. The floor of all 
said stalls must be made impervious to water, and the drainage from said stalls 
must be conducted to the sewer either in tile or cement gutters, of a radius of 
not less than two inches. The said gutters shall discharge into a 3-inch or 
4-inch trap before entering the main sewer. The trap must be protected in all 
cases by a strainer and be easy of access for cleaning purposes. 

"Sec. 5. All stables, sheds, barns, stalls, corrals, or stable yards in which 
any horse, mule or cow is kept shall be thoroughly cleaned out at the following 
intervals of time : Where stables, barns, sheds, stalls, corrals, or stable yards 
exist, they shall be cleaned out at least every day. The manure, offal, soiled 
straw or other refuse matter from all stables, sheds, corrals or stable yards shall 



HOUSE FLY CONTROL 203 

be placed immediately upon removal from such stable, barn, shed, stall, corral 
or stable yard in closely covered metal or metal-lined receptacles, and kept 
covered until destroyed or removed from the premises. The contents of such 
receptacles shall be removed therefrom and disposed of at least twice a week." 

Another type of stable ordinance requires a permit for the erection 
and use of stables, etc., and provides for inspection of the same by the 
score card system. The following is suggested by Mr. Carl L. A. 
Schmidt, City Bacteriologist of Berkeley : 

" Section 1. No person, firm or corporation shall own, conduct, operate, 
manage, or maintain any stable for the use of horses, cows or other animals with- 
out first obtaining a permit therefor from the Health Officer in accordance with 
the conditions in this ordinance hereinafter provided, which permit shall be 
posted in a conspicuous place in the stable. 

"Section 2. Any person, firm, or corporation desiring a permit to own, con- 
duct, operate, manage or maintain a stable for the use of horses, cows or other 
animals shall first make application therefor to the Health Officer, stating the 
name and residence of the applicant, the exact location of the stable for which he 
desires a permit and the kind and number of animals to be kept therein. 

"Section 3. Upon receipt of proper application as provided in Section 2 it 
shall be the duty of the Health Officer or his authorized representative to visit 
and inspect the stable for which application has been made, and to report to the 
Health Officer the sanitary condition of the stable on a score card, the form of 
which is hereinafter provided, leaving a duplicate cop} r on the premises inspected. 

"Section 4. The score card used by the Sanitary Inspector as provided in 
Section 3 shall be printed in the following form : 

CITY OF . . . HEALTH DEPARTMENT 
Stable Score Card 



Owner or Manager of Stable 

Location 

No. of horses No. of cows .... No. of other animals 

Board or Private 

Date of Inspection 



Score 
Perfect Allowed 

1. Character of building 10 

If of first class construction of frame or masonry ... 10 

If poorly constructed 5 

If dilapidated 2 

2. Floors, cement with proper gutters and catch basin and 

sewer or cesspool connection 10 

Cement broken 2 

Cement badlv laid 5 

Wood tightly laid 8 

Wood open cracks 

3. Manure box, strictly fly-proof 50 

Manure box, any part open 5 

Manure box, tight without vent 40 

4. Surroundings perfectly clean 30 

If there is water on lot 10 

If there is manure scattered about 3 

If premises are disorderly _5 

100 



204 MEDICAL AND VETERINARY ENTOMOLOGY 

If maggots or fly pupae are found on premises, score will be limited to 49. 
If doors are not properly cleaned, deduct 5 from total. Filthy catch basin, 
deduct 5 from total. 

"Section 5. If, after inspection, the applicant's score shall be over 50, the 
Health Officer shall issue to the applicant a permit, which shall be numbered 
consecutively. If the applicant's score be below 50, the Health Officer shall send 
to the applicant a notice to improve the sanitary condition of his stable so that 
his score shall be above 50 within a period of 7 days. Failure to do this shall 
constitute a violation of this ordinance. 

"Section 6. It shall be the duty of the sanitary inspector to inspect each 
stable within the City of ... at least once every three months or oftener at his 
discretion and to file the score and record of such inspection in the Health Office. 
Two consecutive inspections of any stable showing a score of less than 50 shall 
cause the Health Officer to revoke the permit of the stable, and the person, firm 
or corporation owning, conducting, operating, managing or maintaining such 
stable shall be guilty of violating this ordinance." 

Manure Ordinances. — Inasmuch as 95 per cent of our house flies 
emanate from horse manure, ordinances regulating the disposal of such 
material are imperative. Municipal collection and disposal of manure 
is highly desirable. There is no reason why the city could not require 
that all manure be collected by authorized scavengers. The manure 
isfthen either to be incinerated or properly stored or piled in some 
designated spot. It is far more preferable that a city have one very 
large municipal manure pile and know where it is, than to have 500 
or more smaller heaps in many out-of-the-way places in all parts of 
the city. The manure can be adequately treated in the former case 
and later sold at a price that would assist materially in clearing the 
cost of municipal collection. The following ordinance constructed by 
the writer in cooperation with Dr. J. N. Force of the Berkeley (Cal.) 
Board of Health, is suggested : 

Ordinance No. . . . 

Regulating the Disposal of Manure and Other Refuse Matter from Buildings or 
Yards where Animals are kept uoithin the City Limits of . . . 

Be it ordained by the Council of the City of ... as follows : 

"Section 1. The manure, offal, soiled straw or other refuse matter from all 
buildings or yards where animals are kept shall be collected at least once daily 
and shall be disposed of by one of the following methods : 

(a) Said refuse may be stored in ventilated bins or other receptacle of such 
construction approved by the Board of Health as to prevent the ingress of flies 
and other vermin, said bin to be emptied at least once a week, or 

(6) Said refuse may be removed from the premises at least once a day by an 
authorized scavenger and disposed of in a manner approved by the Health Officer. 

(c) Said refuse may be spread in a layer not over four (4) inches in depth 
on the surface of the ground. 

"Section 2. No manure shall be used for fertilizing purposes within the city 
limits of . . . which has not been rendered free from live maggots or fly pupa? 
by treating with saturating quantities of water at a temperature of 195 deg. 
Fahrenheit, or some other method approved by the Health Officer. 



HOUSE FLY CONTROL 205 

"Section 3. The presence of live maggots or fly pupae in any collection of 
refuse found in the City of . . . shall be prima facie evidence that the provisions 
of this ordinance have not been complied with. 

"Section 4. It is hereby made a duty of the Commissioner of Public Health 
and Safety or any Sanitary Inspector or Police Officer to provide for the inspec- 
tion of all premises where animals are kept in the City of . . . and examine any 
manure or other refuse matter to determine the presence of live maggots or fly 
pupae. 

11 Section 5. (Penalty clause.) 

"Section 6. All other ordinances and parts of ordinances in conflict with this 
ordinance are hereby repealed." 

According to Howard (loc. cit.) the following regulations concerning 
manure are in force in the District of Columbia : 

"Section 3. That manure, accumulated in great quantities; manure, offal, 
or garbage piled or deposited within 300 feet of any place of worship, or of any 
dwelling, or unloaded along the line of any railroad, or in any street or public 
way ; cars or flats loaded with manure, or other offensive matter, remaining or 
standing on any railroad, street or highway in the cities of Washington or 
Georgetown, or in the more densely populated suburbs of said cities, are hereby 
declared nuisances injurious to health ; and any person who shall pile or deposit 
manure, offal, garbage, or any offensive or nauseous substance within 300 feet 
of any inhabited dwelling within the limit of said cities or their said suburbs, 
and any person who shall unload, discharge or put upon or along the line of any 
railroad, street or highway, or public place within said cities or their suburbs 
any manure, garbage, offal, or other offensive or nauseous substances within 
300 feet of any inhabited dwelling, or who shall cause or allow cars or flats 
loaded with or having in or upon them any such substance to remain or stand in 
or along any railroad, street or highway within the limits of said cities or their 
suburbs within 300 feet of any inhabited dwelling, and who shall fail, after notice 
duly served by this board, to remove the same, shall, upon conviction thereof, 
be fined not less than five nor more than twenty-five dollars for every offense." 

Extract from Article IX, Police Regulations : 

"Sec. 10. No person shall remove or transport any manure over any public 
highway in any of the more densely populated parts of the District of Columbia 
except in a tight vehicle, which if not closed must be effectually covered with 
canvas so secured to the sides of the vehicle as to prevent the manure from being 
dropped while being removed, and so as to limit as much as practicable the 
escape of odors from said manure. 

"Sec. 20. Manures may be deposited in pits below the surface of alleys that 
are not less than fifteen feet wide, but the pit must not extend more than four 
feet beyond the building line. The walls must be substantial and water-tight, 
with stone or iron coping, bedded in cement, set fair with the surface of the alley. 
They must be covered with heavy wrought -iron doors, flush with the alley pave- 
ment or surface, sufficiently strong to carry heavily loaded carts or other vehicles, 
and provided with ventilation by means of a flue inside of the stable and extend- 
ing above the roof of the same, and they must be drained by sewer connections, 
as directed by the Inspector of Plumbing." 

Food Ordinances. — Foods must be protected against dust and flies, 
hence merchants dealing in food products must be required to carry out 
such measures. But it is manifestly unfair to compel merchants to 
protect their wares against flies if stable owners who are responsible 



206 MEDICAL AND VETERINARY ENTOMOLOGY 

for the production of the flies are not compelled to do anything to pre- 
vent the same. 

The Berkeley (Cal.) food ordinance includes the following section : 

"Sec. 3^. Every manager, owner, or other person keeping, maintaining or 
being in charge or control of any store, market, stall, shop, bakery, vehicle, or 
other place where any of the foods or food products mentioned in Section 2 and 
Section 3 of this ordinance are prepared for sale, stored for sale, offered for sale 
or sold, or where food which is prepared for immediate consumption is prepared 
for sale, stored for sale, offered for sale or sold, shall cause such food or food 
products to be screened in such manner as to prevent flies and other insects 
from obtaining access to such food or food products, and to prevent handling 
of the same by patrons or prospective purchasers. 

Howard (loc. cit.) cites the following regulation for the District of 
Columbia relating to food : 

"Every manager of a store, market, dairy, cafe, lunch room, or any other 
place in the District of Columbia, where food, or a beverage, or confectionery, or 
any similar article, is manufactured or prepared for sale, stored for sale, offered 
for sale, or sold, shall cause it to be screened effectually, or effectually pro- 
tected by power-driven fan or fans, so as to prevent flies and other insects from 
obtaining access to such food, beverage, confectionery or other article free from 
flies and other insects at all times. Any person violating the provisions of this 
regulation shall, upon conviction thereof, be punished by a fine of not more 
than twenty-five dollars for each and every offence. This regulation shall take 
effect from and after the expiration of thirty days immediately following the 
date of its promulgation." 



CHAPTER XV 



BLOOD-SUCKING MUSCIDS 

(Tsetse Flies, Stable Flies, Horn Flies) 



A. Tsetse Flies 



Family Muscidoe, Genus Glossina 

Habits. — The tsetse flies are commonly regarded as the world's 
most dangerous insects, and this with much reason, for the African 
sleeping sickness, one 
of the most dreaded 
diseases, is transmitted 
by these flies. For- 
tunately, however, the 
tsetse flies are found 
solely in Africa and 
there only in certain 
restricted areas. 

The tsetses are 
typical intermittent 
blood-sucking insects ; 
in this habit both 
sexes partake, and it 
is said that they bite 
not only during the 
day, but also at night 
when the moon is 
bright. Their flight 
is very rapid and 
direct. They occur Fig. 135 
most abundantly along 
heavily wooded watercourses, where big game animals abound, espe- 
cially the African buffalo, antelope, etc. Still other species occur most 
commonly in less thickly wooded dry localities. 

Structural Characteristics. — The tsetse flies 1 belong to the genus 

1 The writer has gathered data for this chapter by an examination of the 
tsetse fly collections and exhibits in the Liverpool School of Tropical Medi- 
cine, the British Museum and the International Hygiene Exhibit held in Dres- 
den in 1911. 

207 




Glossina palpalis (tsetse fly), carrier of African 
sleeping sickness. X 3.6. 



208 



MEDICAL AND VETERINARY ENTOMOLOGY 




Glossina, which includes medium-sized to large flies, — from the size 
of a house fly to that of a blow fly. They are brownish black in color, 
the body is distinctly wasplike, i.e. with constricted waist (Fig. 135) . 

The wings when at rest 
are closed scissors-like 
(not unlike the Texas 
screw worm fly) and pro- 
ject beyond the abdomen. 
The wing venation (Fig. 
136) is characteristic 
"especially in the course 
of the fourth longitudinal 

Fig. 136. — Wing of a Glossina fly. I«, auxiliary vein ; vem - The anterior trans- 

I to VI = first to sixth longitudinal veins ; A, an- verse Vein is verv oblique. 

terior transverse vein ; B, posterior transverse vein ; m* i j • j.t_ e 

C, anterior basal transverse vein ; D, posterior basal I ne bend in the COUrse 01 

transverse vein; 1« 1»1« first, second and third ^g fourth vein, before it 

costal cells; 2, marginal cell ; 6, submargmal cell; '. 

4, diskal cell ; 5, 6, 7, first, second and third posterior meets the anterior trans- 

cells; 8, anterior basal cell ; 9, posterior basal cell ; vprqp V pj n i- oKc;nhi+plv 

10, anal cell. (Nomenclature after Austen.) X 8. v y rse vem > 1S aDSOlUieiy 

diagnostic " (Stephens 
and Christophers). The palpi are more than half as long as the pro- 
boscis, which points bayonet-like in front of the head. The antennal 
arista is plumose only on the upper side (Fig. 137). The mouth parts 
consist of the labium which ensheaths the 
two piercing seta?, — the dorsally located la- 
brum and the inner hypopharynx, as in Sto- 
moxys. The characteristic "onion shaped" 
bulb is conspicuously located at the base of 
the proboscis (Fig. 138). 

Life History. — The tsetse flies are vi- 
viparous, depositing well-advanced larvae ; 
indeed, these are fully grown and pupate 
within a few hours after extrusion. The 
flies are said to have a striking dislike for 
excrementous matter, and the larvae are or- 
dinarily deposited in the root tangles of the 
banana, mangroves and other tropical vege- 
tation. The time required for the pupal 
stage is from six to eight weeks. 

The pupae (Fig. 139) have striking pos- 
terior protuberances of the terminal segments. 
These are so situated as to produce an in- 
closure for the larval stigmata. 

Trypanosomiasis. — The tsetse, or Glossina, flies are most impor- 
tant carriers of the Trypanosoma of warm-blooded animals. The term 
Trypanosomiasis applies to all diseases produced by flagellate Proto- 
zoan parasites of the genus Trypanosoma, and includes such diseases 




Fig. 137. — Antenna of a Glos- 
sina fly, showing arista with 
branched hairs. (Much en- 
larged.) 



BLOOD-SUCKING MUSCIDS 



209 



as African sleeping sickness, nagana, surra, etc. The trypanosomes 
belong to the Class Zoomastigophora and to the order Trypanosoma- 
tida, are miscroscopic, elongate, more or less spindle-shaped, blood, 
lymph or cerebrospinal fluid inhabit- 
ing parasites, found in many species 
of vertebrate animals, from fish to 
man, and apparently not all species 
are pathogenic. At or near the 
middle of these spindle-shaped or- 
ganisms lies an oval or round body, 
the nucleus; anterior to this is usu- 
ally the rather long filamentous ap- 
pendage, the flagellum, which can be 
traced back along the border of a 
flaplike structure, or undulating mem- 
brane, to a body considerably smaller 
than the nucleus, lying in the pos- 
terior end, the blepharoplast (Fig. 16). 
Immediately adjacent to the bleph- 
aroplast there is often a vacuole, 
and distributed throughout the body 
of the trypanosome are distinct chro- 
matin bodies or points. 

The Trypanosoma increase in the FlG - 138 - 
vertebrate host by longitudinal divi- 
sion. Both the nucleus and the blepharoplast divide, and the^.flagel- 
lum splits into two, or in some species a new flagellum originates from 




fMvijruc 



Mouth parts of a Glossina fly. 
X 17. 




Fig. 139. — Pupa? of the Glossina fly. X 4.8. 



the new blepharoplast. Thus, in the latter case, the flagellum is first 
located posteriorly and migrates anteriorly as the organism grows older. 
In Trypanosoma lewisi there may be found a rosette. The develop- 



210 MEDICAL AND VETERINARY ENTOMOLOGY 

mental stages which are undergone in the intermediary hosts are not 
well known, but there is certainly a series of changes undergone within 
the insect host. 

There are also described male forms said to be " excessively slender, 
staining deep blue, with a sharply defined, rather long, chromatin-rich 
nucleus ; more actively motile than other forms ; ' also female forms ' 
with short flagellum membrane, little folded, two or three times as broad 
as other forms ; staining a light blue ; have few or no granules, and the 
nucleus is spherical" (Stephens and Christophers). Besides these 
there are also described indifferent forms, " the most numerous form, 
nucleus not sharply defined and the protoplasm containing numerous 
granules ; " also encysted forms, latent forms and involution forms. 

The first trypanosome was discovered by Valentin in 1841 in the 
blood of the salmon. The name Trypanosoma 1 was given to these 
organisms by Gruby in 1842-43. The attention was not called to try- 
panosomes of mammals until the work of Lewis in 1878, on the parasites 
of the blood of the rat in India. After that followed the dicovery of 
other important pathogenic trypanosomes, e.g. in 1880 Evans discovered 
the trypanosome causing surra in horses ; in 1897 Bruce found the try- 
panosome of nagana, known as the tsetse fly disease. In 1901 Dutton 
found trypanosomes in human blood, and in 1903 Castellani found them 
in the cerebrospinal fluid of negroes in Uganda suffering from sleeping 
sickness. The trypanosomes found by Castellani were supposed to 
be a different species from that of Dutton {Trypanosoma gambiense) 
and were called T. ugandense Castellani, 1903. Kruse later gave to this 
trypanosome the name T. castellanii Kruse. The important discoveries 
of Dutton and Castellani were confirmed by D. Bruce, who found these 
trypanosomes 38 times out of 38 in the cerebrospinal fluid obtained by 
a lumbar puncture in natives of Uganda suffering from sleeping 
sickness, and twelve times out of thirteen in the blood. According to 
the rules of priority applied to nomenclature, the last two specific names 
must give way to Trypanosoma gambiense Dutton, the older term. 

African Sleeping Sickness. — The most important tsetse fly dis- 
ease is African sleeping sickness, the causative organism of which is 
Trypanosoma gambiense (Fig. lb). This disease is endemic in cer- 
tain regions of Africa, particularly the French Congo and the Congo Free 
State, where for several years it has increased in territory and has 
caused great ravages. It has been estimated that between 1896 and 
1906 from 400,000 to 500,000 natives perished from this pestilence. 
Dutton and Todd found that in some villages from 30 per cent to 50 per 
cent of the population was infected. 

Age does not affect the distribution of the malady, since children, 
as young as eighteen months to two years, have been known to be 
infected. Sex does not influence the disease. Occupation and social 

1 Laveran, A., et Mesnil, 1904. Trypanosomes et Trypanosomiasis. 
Paris, xi + 417 pp. 



BLOOD-SUCKIXG MUSCIDS 



211 



position, however, do show a marked influence. The great majority of 
the cases observed are among the agricultural and lower classes. 

The seasons seem not to influence the advance of the disease, but 
because of the long period of incubation or of latency which precedes 
the usual appearance of nervous symptoms, the influence of the seasons 
is hard to determine. 

There are two distinct phases in sleeping sickness. During the 
first phase the trypanosomes are in the blood (Fig. 140), usually in small 
numbers. With the negroes there are said to be no morbid symptoms, 
but with the whites it is manifested by an irregular fever. Glandular 
enlargement is an early and constant feature, and the trypanosomes are 
practically always found in 




the enlarged glands. In the 
second place, the trypano- 
somes are constantly found 
in the cerebrospinal fluid ; 
there is nervousness and 
trembling until drowsiness 
appears, the fever taking on 
the hectic character. Drow- 
siness gives way to lethargy, 
and finally the victim falls 
into a comatose state. 

The first stage may last 
several years, while the 
second is from four to eight 
months' duration, exception- 
ably one year. 

The description of the 
trypanosome is given by 
Stephens and Christophers, 
viz.: " 12-28 by 1.5-3 rnicra. 
The blepharoplast is oval. There is not uncommonly a vacuole in 
close association with it. The trypanosome, at least in animals, oc- 
curs in two main forms, a long and a short." Glossina palpalis, a 
tsetse fly, and its varieties, is unquestionably the principal, if not the 
sole, agent of transmission. After inoculation into the human the 
incubation period varies, it is said, from several months to several years. 

A second species of trypanosome producing African sleeping sickness 
in Rhodesia, Xyasaland and adjoining territory is T. rhodesiense (Ste- 
phens and Fantham) } In this trypanosome the nucleus is usually in the 
blepharoplast end of the parasite. The carrier is Glossina morsitans. 



Fig. 140. — Photomicrograph of a blood smear, 
showing Trypanosoma gambiense of African sleep- 
ing sickness. X 625. 



1 Stephens, J. W. W., and Fantham, H. B., 1913. Trypanosoma rhode- 
siense (Stephens and Fantham), a second species of African trypanosome pro- 
ducing Sleeping Sickness in man. Trans. Fifteenth Internat. Cong. Hyg. and 
Dem., Vol. 5, Pt. II, pp. 615-619. 



212 MEDICAL AND VETERINARY ENTOMOLOGY 

Transmission. — The natives of French Guinea long attributed the 
power of disseminating sleeping sickness to flies and it had already 
been shown that nagana, a disease of horses and dogs, was transmitted 
by tsetse flies when Dutton and Todd studied the biting flies of Gam- 
biense. These investigators found that of the flies wilich bite man and 
animals, Tabanus dorsovittata and Glossina palpalis were the most impor- 
tant, the latter being very common in western Africa, where it abounds in 
the mangroves which line the rivers and water banks during the warmer 
months when these insects are very troublesome. Experiments, how- 
ever, made by these workers gave negative results. It was Bruce and 
his collaborators who subsequently went over the matter and showed 
that Glossina paljjalis is the principal agent of transmission. Other 
tsetse flies known to transmit sleeping sickness are Gl. palpalis var. 
wellmani, Gl. fusca, also Gl. morsitans. 

Animal experimentation indicates that these flies can transmit the 
causative protozoon mechanically for a period of less than forty-eight 
hours, though the organisms become more and more attenuated after 
the fly has bitten the diseased individual and loses its power of infection 
in less than forty-eight hours. Thus the tsetse fly proves itself a me- 
chanical carrier for only a few hours during which time its soiled proboscis 
is involved, i.e. trypanosomes are injected into the w T ound produced by 
the bite before the proboscis is cleaned. 

It is, however, well known that trypanosomes taken into the stomach 
of the fly pass through a metamorphosis, developing into two forms 
known as male and female. These latter give way to an indifferent type 
and in from four to five days all trypanosomes disappear. Recent 
experimental evidence indicates that the flies become infective once 
more at the end of about four weeks, and then appear in the salivary 
glands of the insects. Nuttall x states that the trypanosomes appear 
in the salivary glands of the fly after a period of twenty-five to twenty- 
eight days following the infective meal. During this interval, except 
as noted above, the flies are incapable of producing infection. The 
parasites in the salivary glands of the fly resemble T. gambiense as seen 
in the mammalian blood and they persist as long as the fly lives. 
The Sleeping Sickness Commission has found that infectivity lasts at 
least ninety-six days. The life of a female Gl. palpalis in captivity has 
been observed to be about four and one half months. The same author 
(Nuttall) states that injections of either the gut content or salivary gland 
emulsion produce infection after about the twenty-fifth day. Under 
laboratory conditions only about 5 per cent or 6 per cent of the flies 
become infective. 

The Question of Reservoirs. — Inasmuch as infective flies have 
been taken in regions uninhabited by man for at least three years, there 
must be some other animal or animals in which the trypanosome of 

1 Nuttall, G. H. F. The Herter Lectures : II, Trypanosomiasis, Parasit- 
ology, Vol. V, No. 4, pp. 275-288. 



BLOOD-SUCKING MUSCIDS 213 

sleeping sickness is preserved in an infective state. This seems further 
more imperative since no evidence is at hand that the trypanosomes are 
transmitted from the parent fly to the offspring, i.e. hereditarily. There 
is now sufficient evidence at hand to prove that the African antelope 
serves as a perfect reservoir for the trypanosome, 1 that these animals 
recover from the experimental infection and therefore serve as " chronic 
carriers." Many animal? may serve as reservoirs. (See Nuttall, 
1913, he. cit.) 

Nagana. — As sleeping sickness is to man so is nagana to domesti- 
cated animals, especially horses and dogs. Trypanosoma brucei Plimm 
and Bradf . is the causative organism of nagana, which malady was early 
known as the fatal tsetse fly disease of African horses and mules, less 
fatal in cattle and sheep. The disease is characterized by progressive 
emaciation, fever, oedema of the abdomen and genitalia and marked 
depression. The trypanosomes are found in the blood and especially 
the lymph gland swellings from the beginning of the first symptoms. 

The trypanosome is described by Stephens and Christophers, viz. : 
" 26-27 micra in rats, 28-33 micra in horses. The nucleus lies almost 
in the middle. The blepharoplast is almost quite round. The flagel- 
lum is generally separated from it by a slight interspace." 

For some years nagana was known as the tsetse fly disease. Glos- 
sina morsitans and Gl. longipalpns relate to its transmission in practi- 
cally the same way as does Glossina palpalis to sleeping sickness, i.e. 
the fly is infective for three or four days after feeding on an infected 
animal, then becomes non-infective for a period of about three weeks and 
then again becomes infective, remaining so for the rest of its life. The 
incubation period after inoculation into the body of the host is said to 
be about ten days. 

Control of the Tsetse Fly Disease. — Thus far little progress has 
been made in the treatment or immunology of tsetse fly diseases ; upon 
the latter no doubt rests the ultimate solution of the problem. A ready 
means for the destruction of the flies is unknown. Although numerous 
flies may be destroyed by catching them with sticky substances such 
as birdlime, their reduction is hardly if at all noticeable. Repellents, 
though many have been tried, give poor results ; oil of citronella seems 
to be of some value. The general and practical control of breeding 
places offers unsurmountable difficulties owing to the fact that the 
larvse are retained within the body of the female, hence are not directly 
dependent upon an external supply of food. Starving the adult flies by 
eliminating wild animals upon which they are dependent for blood is a 
method employed experimentally in many localities. The wide range 
of food animals, the question of reservoirs and the need of domesticated 
animals reduces this method to one of secondary importance to be em- 
ployed in association with other methods. 

A study of the habits of the tsetse shows that villages located in 
i See Proc. Roy. Soc., Series B, vol. 83, pp. 513-527, 1911. 



214 MEDICAL AND VETERINARY ENTOMOLOGY 

the midst of extensive clearings and not too near water courses are 
largely free from these insects. The clearings should be from 400 to 
600 yards in width and can best be maintained by placing them under 
cultivation (rice and larger shade-producing vegetation excepted). 
Wells should be utilized for water supply. 

Screening is an important adjunct to the control of sleeping sickness. 
Dwellings, trains, steamers and other conveyances should be carefully 
screened. 

The use of veils, gloves and loose white garments is highly recom- 
mended. 

Since the tsetse fly diseases spread along trade routes and extend 
from infected centers, there is an obvious demand for the control of 
transportation to prevent as far as possible the employ of infected 
individuals. 

Owing to the complicated colonial situation in Africa, both geo- 
graphically and commercially, the control of trypanosomiasis calls for 
hearty cooperation among the powers concerned. 

Systematic. — All flies belonging to the genus Glossina partake 
of the following characteristics : medium-sized flies from size of house 
fly to blowfly, dark brownish in color ; wings when at rest folded scissors- 
like over the back, longer than the abdomen ; fourth longitudinal vein 
bends sharply before meeting the anterior transverse vein; proboscis 
when at rest projecting horizontally in front of the head ; the base of 
proboscis is provided with an onion-shaped bulbous expansion; the 
arista is plumed on upper side. 

The following species * may be mentioned : 

(1) Glossina palpalis Robineau-Desvoidy is a medium-sized tsetse 
fly from 8 to 9 mm. in length. Its general color is light brown with 
a dusting of gray. The antennae are dusky, the arista has 18 aristal 
hairs. The thorax heavily dusted with gray and has dark lines and 
spots. The abdomen is light brown beneath dusted with gray; 
above it is nearly black with a longitudinal, median narrow light brown 
stripe. The halteres are white. The legs are light brown with indistinct 
dark spots on the tarsi. The hind tarsi are black. 

This species is found throughout West Africa from the Congo to the 
Senegal, wherever there is water. 

Glossina palpalis var. ivellmani Austin varies from the above in that 
it has a yellowish brown frontal stripe, and tarsi nearly white. It occurs 
in Angola. 

Glossina morsitans Westw. is said to be almost identical with Glossina 
longipalpus, except that it is ordinarily somewhat smaller. Grunberg l 
declares that it would be more correct to consider morsitans as a variety 
of longipalpus. Furthermore, because of the fact that both species are 

1 Griinberg, Karl, 1907. Die Blutsaugenden Dipteren. Verlag yon Gus- 
tav Fischer in Jena, vi + 188 pp., 127 figures. (The above descriptions of 
tsetse flies are adapted after this author.) 



BLOOD-SUCKING MUSCIDS 



215 



transmitters of nagana, the separation of the two species has no practical 
value. 

The distribution of this species coincides with that of Gl. longipalpus, 
though it is ordinarily attributed to a much greater portion of Africa, 
because its habitat consists of less heavily wooded and drier areas. 

Glossina longipalpus Wiedem. is also a medium-sized fly ranging from 
8-10 mm. in length. The color is light brown with very little gray. 
The antenna? are dark brown, the arista is light brown with 25 aristal 
hairs. The palpi are light brown, tipped with black. The thorax is 
heavily dusted with gray. The abdomen is light brown, marked dor- 
sally, to the right and left, on the 2-6 segments with black semilunar 
lateral spots, resting broadly on the proximal end of each segment. 
The hal teres are white. The legs are light brown with black tipped 
pro- and meso-thoracic tarsi ; the hind legs are black. 

This species occurs in Sierra Leone and British Central Africa. 

Other species of Glossina flies are the following : GL pallicera with 
20-22 aristal hairs (Grunberg) ; Gl. pallidipes with 25 aristal hairs 
(Grunberg) ; GL longipennis with 18-20 aristal hairs (Grunberg) ; 
and GLfusca, a large species (11-13 mm.) also with 18-20 aristal hairs 
(Grunberg). 

B. Stomoxys or Stable Flies 

Family Muscidce, Genus Stomoxys 

General Characteristics. — Owing to similarity in color and size 
(Fig. 141) the Stomoxys fly is often mistaken for the common house fly, 




Fig. 141. 



(a) The common house fly (Musca domestica) 
calcitrans). X 2.5. 



(b) the stable fly (Stomoxys 



Musca domestica. However, the former is more robust with broader 
abdomen. In color it is brownish gray with a greenish yellow sheen ; 
the outer of the four longitudinal thoracic stripes are broken and the 



216 MEDICAL AND VETERINARY ENTOMOLOGY 

abdomen is more or less checkered. The wings when at rest are widely 
spread apart at the tips, are distinctly iridescent and the apical cell is 
open. When resting the fly has its head thrown well up and the wings 
slope decidedly toward the surface upon which it has settled. The 
proboscis protrudes bayonet-like in front of the head. The antennal 
arista, unlike the house fly, bear setae on the upper side only (Fig. 29). 

Habits. — Although the Stomoxys fly is commonly called the stable 
fly, it occurs much less abundantly (often absent) about stables than does 
the house fly. " Biting house fly " is a term often applied, since the fly 
commonly occurs indoors especially in the autumn and during rainy 
weather. The Stomoxys fly is typically an out-of-door fly and is usually 
to be found in summer where domesticated animals occur, especially 
cattle. Its occurrence around stables is traceable to the presence of 
cattle or horses usually, and not to the presence of manures directly. 
Sunny fences, walls, light-colored canvas coverings and light objects in 
general when in the proximity of cattle are abundantly frequented by 
Stomoxys flies. 

The Stomoxys fly is a vicious " biter," draws blood quickly and 
fills up to full capacity in from 3 to 4 minutes if undisturbed, but ordi- 
narily even when undisturbed changes position frequently or flies to 
another animal, where the meal is continued. This fly feeds readily on 
many species of warm-blooded animals, for example, rats, guinea pigs, 
rabbits, monkeys, cattle, horses and man. Both sexes are blood-suck- 
ing. The flight of the Stomoxys fly is direct and swift. 

Light Reactions. — The Stomoxys flies respond positively and 
strongly to light, being much more responsive to this stimulus than 
house flies, hence the former are normally out-of-door flies, while the 
latter are house flies, responding readily to odors emanating from the 
house. Because of the strong positive reaction to light these flies can 
easily be transferred from breeding jars to other receptacles by covering 
the former with black cloth, leaving an opening toward the light into 
which opening a test tube is inserted. Hundreds of flies can thus easily 
be transferred in a few minutes. Observations on the photic reactions 
of these flies bid fair to give very interesting results. 

The larvae, like those of flesh flies and house flies, are decidedly nega- 
tive to light. In breeding these flies, the larvae must be supplied with 
sufficient material so that they can bury themselves deeply, — they are 
thus protected against light, and enough moisture must be applied to 
keep the mass of material in a " soggy " condition. . Too much mois- 
ture is, however, destructive. 

Breeding Habits and Life History. — Although the Stomoxys fly 
can successfully be reared in the manures of horses, cattle, sheep, etc., 
it may be safely said that it does not breed commonly in excrement under 
field conditions unless straw or hay predominates. For every thousand 
house flies bred in horse manure, there are, as a rule, not more than one 
or two Stomoxys flies. The very best breeding places are afforded by 



BLOOD-SUCKING MUSCIDS 



217 



the left-over hay, alfalfa or grain, in the bottoms or underneath out-of- 
door feed troughs in connection with dairies (Fig. 142). This material 




Fig. 142. — A feed trough for dairy cattle which furnishes an ideal breeding place for 
Stomoxys flies. The moist lower layers of material in the trough furnish abundant 
food for the larva?. 

soon becomes soggy and ferments, and here practically pure cultures of 
Stomoxys larvae may be procured. The material must be moist ; dry- 




Fig. 143. — Showing posterior larval spiracles of Stomoxys calcitrans (left) ; Musca 
domestica (right). X 21. 

ness prevents development. Piles of wet fermenting weeds and lawn 
cuttings also furnish fairly good breeding material. Piles of - decaying 



218 MEDICAL AND VETERINARY ENTOMOLOGY 

onions have been found by the writer to harbor myriads of larvae late 
in autumn. 

The larvae of Stomoxys and of the house fly can readily be differen- 
tiated by the form, size and position of the posterior spiracles (Fig. 143), 
otherwise they resemble each other closely. The pair of posterior spir- 
acles of the Stomoxys larva are roughly triangular, widely separated and 
situated near the periphery, while in the house fly larva they are ellip- 
tical, quite large, close together and more central in position. 

The eggs of the Stomoxys fly are about 1 mm. long, curved on one 
side, straight and grooved on the opposite side. In depositing her eggs 
the female fly often crawls far into the loose material, depositing her 
eggs usually in little pockets in small numbers, often in pairs. Egg 
depositions range in number from 23 to 102, usually between 25 and 
50, and there are ordinarily four or five layings. Mitzmain 1 has 
found in his observations made in the Philippine Islands that the maxi- 
mum number of eggs produced by a single Stomoxys is 632 and possibly 
820, and that there may be as many as twenty depositions during the 
lifetime of the female. 

The incubation period varies from two to five days, commonly three 
days, at a temperature of 26° C. Higher temperatures result in a shorter 
incubation period. The newly hatched larvae bury themselves in their 
food at once, thus protecting themselves against light and dryness. At 
a temperature of from 21° to 26° C. the larvae reach full growth in from 
fourteen to twenty-six days. Mitzmain (loc. cit.) found that the larval 
stage averaged twelve days at a room temperature of 30° to 31° C. 

Before pupation the larvae usually crawl into the drier layers of the 
breeding material, where the chestnut-colored pupae are often found in 
enormous numbers. The pupae are from 6 to 7 mm. long and may be rec- 
ognized by the posterior spiracles as in the larva. The pupal period again 
varies, dependent on temperature especially. At a temperature of from 
21° to 26° C. this period varies from six to twenty-six days, with the 
greatest frequency between nine days and thirteen days (Table XII). 



TABLE XII 

Table Showing Day of Emergence op Stomoxys Calcitrans after Day 
of Pupation. Larvae Pupating in an Insectary at a Temperature 
of from 21° to 26° C. 





Pupal 






































Period in 


6 


7 


8 


9 


10 


n 


12 


13 


14 


15 


16 


17 


18 


19 


20 


21 


Totals 




Days 




































A 


No. flies 


1 


2 


42 


108 


424 


167 


85 


15 


8 


4 


2 













858 


B 


No. flies 


3 


10 


12 


80 


200 


70 


20 


16 


10 


19 


4 


3 











427 


C 


No. flies 


20 


125 


85 


100 


200 


70 


120 


50 


75 


30 


20 


30 


40 


15 


4 





887 



1 Mitzmain, M. B., 1913. The bionomics of Stomoxys calcitrans Linnaeus; 
a preliminary account. The Philippine Journal of Science, Vol. VIII, No. 1,. 
Sec. B., pp. 29-48. 



BLOOD-SUCKING MUSCIDS 



219 



At an average temperature of 29° C. Mitzmain (loc. cit.) found the 
pupal period to average five days. 

If not handicapped, the imago emerges with astonishing rapidity, 
crawls away, unfolds its wings and is ready to fly away in less than half 
an hour. The fact that the proboscis is temporarily attached beneath 
the thorax gives the newly emerged insect a very peculiar appearance, 
and it may then be easily mistaken for a house fly. 

Summarizing the life history of the Stomoxys fly (Fig. 144) it may be 
said that at a temperature of 21° to 26° the shortest periods are : egg, 
two days, larva, fourteen days, pupa, six days, total twenty-two days; 
the average, egg, three days, larva, fifteen days, pupa, ten days, total, 
twenty-eight days ; the maximum, egg, five days, larva, twenty-six days, 
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(Photo by H. F. Gray.) X 2. 

from the laying of the egg to the emergence of the imagines was from 
thirty-three days to thirty-six days as observed in five individual cases. 
Mitzmain (loc. cit.) reports the development of this fly in twelve days 
under optimum conditions. 

Copulation takes place within a week and egg deposition begins^in 
about eighteen days after emergence from the pupa cases at a temper- 
ature of from 21° to 26° C. Higher temperatures. undoubtedly decrease 
this time. 

Longevity. — With approximately 4000 flies under continuous daily 
observation in glass quart jars, 50 flies to a set, the writer has found that 
the average length of life of the Stomoxys fly under favorable condi- 
tions of feeding (i.e. daily feedings on monkeys or rabbits) is about 
twenty days. The maximum life under these conditions was found to 
be sixty-nine days and several hours, — observed in a female (Fig. 145) . 

Mitzmain (loc. cit.) has found the maximum for a female fly to be 
seventy-two days and for the male ninety-four days. 

The writer has observed that a set of flies which fed only on sugar 
water deposited no eggs, although many of them lived twenty days or 



220 MEDICAL AND VETERINARY ENTOMOLOGY 



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BLOOD-SUCKING MUSCIDS 221 

longer, while control flies fed on blood did lay eggs. Hence it seems 
apparent that the flies must have blood in order to develop eggs. 

As a Cattle Pest. — In a most useful and interesting paper on the 
stable fly, as a live stock pest, Bishopp x regards this fly as very impor- 
tant. Injury is brought about in various ways, e.g. worry, due to the 
attacks of myriads of flies ; loss of blood ; lessening of the milk supply 
from 40 to 60 per cent ; loss of flesh ; bringing on attacks of acute 
Texas fever if the cattle are already parasitized ; etc. 

Surra. — Surra is one of the most important diseases of horses in 
the Philippine Islands, and its spread on these islands behooves the 
government to a most careful consideration of its transmission. The 
causative organism is Trypanosoma evan-si (see Chapter XII) which is 
harbored by a number of hosts, mainly horses, in which the disease is 
highly fatal, also mules and the carabao, and experimentally in monkeys. 
guinea pigs and rabbits. 

The Stomoxys fly has been regarded by some authors as an impor- 
tant carrier of this trypanosome. Unfortunately there is little or no 
conclusive experimental evidence in favor of this theory. Mitzmain 2 
in a most important contribution on this subject presents very good evi- 
dence that this fly need not be regarded as a factor in the transmission 
of surra, that its spread is attributable mainly to a horsefly, Tabanus 
striatus, the common horsefly of the Philippine Islands. In a letter to 
the writer Mitzmain states that Stomoxys calcitrans was used daily on 
clean animals up to ninety-four days after removal from the infected 
hosts without successful transmission. 

Poliomyelitis. — Poliomyelitis, also known as infantile paralysis, 
was first described in 1820 in Norway, and it seems quite likely that the 
spread of this disease is traceable to immigrants from the Scandinavian 
peninsula. Severe epidemics of this disease are apparently not recorded 
until recent years, the latter few years of the last century and the 
beginning of this. 

Apparently the first epidemic to be reported in the United States 
was in 1891 in Vermont, and a year later a small epidemic was reported 
in California. During the past five years the disease has been spreading 
to an alarming extent. In 1907 over 2500 cases occurred in New York 
State, in 1909 nearly 1000 cases in Massachusetts and over 600 cases in 
Nebraska ; in California for the year beginning November 1, 1911, and 
ending October 31, 1912, there were 495 cases with a mortality of 23.3 
per cent. Children between the ages of three and four seem to be most 
susceptible to the disease and the mortality is highest between these 
ages. The disease is, however, not restricted to infants, since adults 
are known to show characteristic symptoms. 

The symptoms of the disease in the first stage are vague, — there is 

1 Bishopp, F. C, 1913. The stable fly (Stomoxys calcitrans L.), an important 
live stock pest. Journ. Eeon. Ento., Vol. 6, No. 1, pp. 112-127. 

2 Mitzmain. M. B., 1913 (loc. cit). 



222 MEDICAL AND VETERINARY ENTOMOLOGY 

fever, nervousness, gastric and intestinal disturbances, loss of appetite 
and headache ; these symptoms are followed by the more definite condi- 
tions of paralysis of arms and legs, usually asymmetrical, trembling and 
finally complete paralysis. Death often occurs through paralysis of the 
diaphragmatic muscles. If recovery takes place, often months elapse 
before complete use of arms and legs is regained. 

The causative organism is unknown, but is filterable and hence 
belongs to that already large group of ultra-microscopic organisms, 
including those of yellow fever and dengue. The incubation period in 
the human has not been ascertained, but in monkeys it is as short as 
three or four days and in these animals death often ensues in five days. 

The epidemiology of Poliomyelitis is complicated. The virus is 
known to retain its virulence under most adverse conditions, said to 
remain virulent in dust (Neustaedter and Thro). 1 The disease can 
be produced by painting the nasal mucosa with the virus. All this 
would seem to point toward ease of transmission and infection, which 
is really not the case, otherwise epidemics of this disease in schools would 
be common occurrences. Again, healthy monkeys caged with monkeys 
infected with the disease do not readily become infected by contact. 
Notwithstanding these facts cases are cited in which the disease has 
been transmitted by contact. On the other hand cases are numerous 
in which the patients are far separated from other cases. 

Because of this peculiar distribution the attention of investigators 
has been called to the possibility of insect transmission. The following 
quotation is taken from the California State Board of Health Special 
Bulletin on Poliomyelitis (October 15, 1912). 

'•'In 1909,, Dr. J. H. Hill. Epidemiologist of the Minnesota State Board of 
Health, presented the apparent relation of dusts to the occurrence of the disease 
and its frequent appearance on premises having accommodations for horses and 
other animals. 

" Professor W. B. Herms, of the University of California, has for several 
j^ears considered the "biting fly" [Stomoxys calcitrans) to be a possible factor in 
transmitting the disease. 

"Dr. M. W. Richardson. Secretary Massachusetts State Board of Health, in 
1911 was one of the first workers to begin the systematic collection of insects 
found on the premises of poliomyelitis cases. His observations and his strong 
suspicion of the "biting fly" based upon fin cling this species of fly as the only 
insect constantly present in the majority of houses where poliomyelitis had 
occurred, were presented to the American Public Health Association in Havana 
in December. 1911. 

"Dr. Flexner of the Rockefeller Institute for Medical Research and his as- 
sociates, in their several progress reports on Poliomyelitis have. pointed out 
the possibility of insects being a factor in disseminating the disease, and have 
emphasized the fact that if this could be proved it would explain many of the 
difficult points in its epidemiology. 

"Doctor Frost of the United States Public Health Service has been con- 
stantly observing the epidemiological factors in American outbreaks of polionry- 

1 Neustaedter. M., and Thro, W. C. N. T. Med. Journ., 1911, XCIY, 
p. 813. 






BLOOD-SUCKING MUSCIDS 223 

elitis during the past three years, in an effort to collect evidence supporting or 
disproving the efficiency of administrative measures that have hitherto pre- 
vailed. 

"In the summer of 1912, Dr. Richardson continued his work and Dr. M. J. 
Rosenau of Harvard University began a series of scientific experiments to 
demonstrate if possible, whether poliomyelitis can be transferred from infected 
monkeys to well monkeys through the agency of the "biting fly" (Stomoxys 
calcitrans). In a preliminary scientific announcement, September 26, 1912, 
before the International Hygienic Congress, Dr. Rosenau stated that he had 
succeeded in accomplishing this in his first series of experiments." 

The following is quoted from a report of Rosenau' s w r ork in the 
Journal of the American Medical Association (Vol. LIX, No. 14, p. 1314) 
under " Proceedings of the International Congress on Hygiene and 
Demography." 

"In reference to the transmission of poliomyelitis by the biting fly, we were 
led to focus our attention on this biting fly (Stomoxys calcitrans) as an inter- 
mediate host in the transmission of a particular infection referred to by Dr. 
Richardson. When I first began to stud} 7- the disease, I regarded it probably 
as one which is spread by direct contagion, by contact, either directly or in- 
directly, from person to person. The first circumstance which shook my faith 
that we were dealing with a contagious disease was the fact .that we had eighteen 
negative results in attempting to prove the presence of the virus in the secretions 
from the nose and throat. I could not help asking at the time if it were not 
possible to find the virus, which is so potent, in the secretions of the nose and 
throat of persons who have the disease and those who are convalescing from 
the disease. These results were confirmed at the same time by Strauss, of 
New York, who had negative results in a large series and by Neustaedter's 
recent results and by other results, all of the examinations having proven nega- 
tive excepting one recently reported by Kline, Patterson and his associates at 
this congress and in the literature recently. 

"A second circumstance which led me to believe we were not dealing with a 
contagious disease was the fact brought out by Dr. Richardson. Children in 
all stages of this disease were crowded into schools, institutions, tenement 
districts and other places where there was every chance for the spread of the 
disease, but it did not spread there, but it continued to spread in the rural, 
thinly scattered districts where one would not expect to find contagious disease. 
There was a resemblance to rabies. All those who have worked with this virus 
in laboratories were at once struck with the resemblance between poliomyelitis 
and rabies. The latter being a wound infection, there is some analogy between 
it and poliomyelitis, and poliomyelitis might be transmitted through some sort 
of wound. I was fortunate enough to have had experience with yellow fever, 
both in the investigation of it and the sanitary measures against it, before the 
mosquito period, and I was much struck with many analogies which came to me 
between that disease and certain features of poliomyelitis. 

"The work I bring to your attention consisted of taking a number of flies, — 
Stomoxys calcitrans, — caught in a net and bred for the purpose ; you can catch 
several hundred of these flies in a stable in a very short time. We placed these 
flies in a large cage and exposed monkej^s to their bites, the monkeys having 
been purposely infected with the virus of poliomyelitis. Care was taken to 
place the monkeys in the cages in all stages of the disease, before and after. 
In fact a monkey would be exposed to the bites- of the flies on the same day he 
was infected, so that the flies could drink the blood of the monkey during all 
stages of the period of incubation of the disease, for we do not yet know in what 



224 MEDICAL AND VETERINARY ENTOMOLOGY 

stage of the infection the virus appears in the blood at its maximum, or the best 
period for infecting these flies. Following this we exposed healthy monkeys to 
the bites of the same flies, and after several weeks' time these healthy monkeys 
came down with a disease which in all essential respects resembles anterior 
poliomyelitis. Out of twelve healthy monkeys so exposed, six of them now have 
symptoms of the disease, three of them in the virulent form. Of the other three 
monkeys, two are coming down, but one seems to have a milder infection than 
the other. This mild infection consists of trembling and weakness of the hand, 
and some weakness of the jaw which lasted about a week or so and then passed 
away. We cannot be sure whether that is true poliomyelitis or not until we 
are able to test the monkey subsequently. If it were poliomyelitis, that monkey 
will be 'immune.' In three of the six cases that came down with the disease, 
having been bitten by flies, there was some diarrhea. The disease in the monkey 
resembles more closely that which we see in children, rather than the disease we 
produce purposely experimentally by bringing the virus in direct association 
with the central nervous system. Of course, that may be only a coincidence, but 
it is interesting." 

The work of Rosenau was repeated and confirmed during October, 
1912, by Anderson and Frost * who summarize as follows : " Three 
monkeys exposed daily to the bite of several hundred Stomoxys, which 
at the same time were allowed daily to bite two intracerebrally inocu- 
lated monkeys developed quite typical symptoms of poliomyelitis eight, 
seven and nine days from the date of their first exposure." 

In order to verify the findings of the above experiments and to 
secure further biological evidence if possible the writer, in cooperation 
with Dr. W. A. Sawyer, 2 undertook a special investigation of the 
problem, beginning in October, 1912. Believing it unwise to use flies 
collected out of doors these insects were reared for the purpose in an 
insectary. The importance of this precaution is made evident by the 
fact that flies captured out of doors in Berkeley were shown to transmit 
a pathogenic organism to a rabbit, infection undoubtedly having been 
acquired in nature. This infection resulting in abscess was successfully 
transmitted from rabbit to rabbit through the agency of the Stomoxys 

"In Rosenau's announcement he stated that the monkeys showed symptoms 
of poliomyelitis several weeks after the flies, which were biting them frequently, 
had had their first opportunity to receive infection from sick monkeys. This 
would allow abundant time for a definite biological change in the virus, prepar- 
ing it, during the incubation in the fly as intermediate host, for successful 
inoculation into the w r arm-blooded monkey. Such a process seemed not an 
improbable explanation of the results when we considered that Rosenau was 
dealing with a blood-sucking insect and a disease in which the blood had been 
shown to have very low infectivity on direct inoculation. The symptoms of 
poliomyelitis in the experiments of Anderson and Frost appeared so soon after 

1 Anderson, John F., and Frost, Wade H., 1912. Transmission of polio- 
myelitis by means of the stable fly (Stomoxys calcitrans). U. S. Pub. Health 
Repts., Vol. XXII, No. 43, Oct. 25, 1912. 

2 Sawyer, W. A., and Herms, W. B., 1913. Attempts to transmit polio- 
myelitis by means of the stable fly (Stomoxys calcitrans). Journ. Amer. Med. 
Assoc, Vol. LXI, pp. 461-466. 



BLOOD-SUCKING MUSCIDS 225 

the first possible transference of infectious material that in all probability the 
process consisted of a mechanical transference of blood or other infectious 
material taken up by the flies while repeatedly piercing the skin. The extreme 
shortness of time available, in their experiments, for incubation of the virus in 
the fly is apparent when we consider that, in the interval of nine or ten days, 
we must allow also for the development of the virus in the original inoculated 
monkeys and for the incubation period in the monkeys infected by the flies." 
(Sawyer and Herms, loc. cit.) 

Assuming the accuracy of the work of Rosenau and Anderson and 
Frost, it seemed advisable to plan the experiments so as to secure, if 
possible, an answer sooner or later to each of the following questions : 

1 . Is the Stomoxys fry merely a mechanical carrier of poliomyelitis or is it an 

intermediary host ? 

2. If it is an intermediary host how much time must elapse after biting before 

it can infect another animal ? 

3. How long does the fly remain infective? 

4. How soon after infection does the experimental animal become infective to 

the fly and how long does the animal remain infective to the fly ? 

5. Does the severity of the infection increase with the number of bites of the 

fl y ? . 

6. What is the percentage of infected flies in nature ? 

7. Do other biting insects carry this disease ? 

8. Can other animals be inoculated by the Stomoxys fly and serve as carriers 

or receptacles of the disease, e.g. chickens, rabbits, guinea pigs, rats, mice, 
pigs, dogs, cats, horses and cattle? 

9. What are the best methods to exterminate the Stomoxys fly ? 

10. What precautions are necessary to prevent the existing flies from coming 
in contact with infectious patients and carrying the disease to other 
individuals ? 

A series of seven experiments was conducted covering a period of 
about nine months and involving the use of about four thousand labora- 
tory reared flies, a large number of monkeys, rabbits and other rodents. 
The experiments were carefully planned and every precaution was taken 
to bring about accurate results. In the first experiment approximately 
1750 flies were used, applying these to the animals in bobbinet-covered 
glass jars (quarts), 50 flies to a set (Fig. 146). A rhesus monkey was 
inoculated intracerebrally with 2 cc. of a suspension of Flexner virus, 
and the first set of flies was placed on this animal immediately after 
inoculation and after ten minutes' feeding transferred to a healthy 
monkey. The next day new sets of flies were used and again trans- 
ferred to the same monkey, and those flies which had bitten the sick 
monkey on the previous day (24 hours ago) were placed to bite another 
unused monkey. In this way new flies were used each day and trans- 
ferred immediately to the first healthy monkey; thus this animal al- 
ways received flies that had fed for the first time on the sick monkey and 
transferred immediately. The second healthy monkey always received 
flies supposed to hold infection for 24 hours ; the third animal, flies of 
48 hours standing ; the fourth animal, flies of four days ; the fifth animal, 



226 



MEDICAL AND VETERINARY ENTOMOLOGY 



flies of nine days ; the sixth animal, flies of seventeen days ; the seventh, 
flies of thirty days; and the eighth received daily all the survivors of 
the entire series until all the flies were dead. 

Between monkey feedings until the last animal was used, the flies 
were kept alive by allowing them to feed on rabbits every other day, 
a new rabbit being used each time. The rabbits remained healthy. 

In the above experiment all the monkeys remained healthy except 
two ; namely, the first one which received the virus, and that animal died 
on the fourth day of typical poliomyelitis, and the seventh animal, which 
died of acute pneumonia. 

Except in cases of immediate transfer when only ten minutes of 
feeding was permitted, the flies were given ample opportunity to feed 




Fig. 146. — Showing jar method of feeding Stomoxys flies on monkeys. The jars are 
covered with bobbinet and sealed with adhesive plaster. The flies thrust their probos- 
cides through the meshes and thus come in contact with the monkey. 



until satisfied (normally from 20 to 30 minutes) and ordinarily the flies 
fed well. 

In the second experiment an immobilized inoculated monkey was 
placed in a screened fly cage (16" X 28" X 18") with 500 Stomoxys 
flies. This animal remained in the cage with the flies for two hours, 
after which it was removed and a healthy monkey substituted (also 
immobilized). The second animal remained in the cage with the 
flies also for a period of two hours. This was repeated daily until the 
inoculated monkey died of poliomyelitis, after which the healthy animal 
was returned to the cage daily until all the flies were dead. The results 
proved negative. 

In the third experiment the flies in jars as before to the number of 
about 600 were kept continuously under higher temperatures in the 



BLOOD-SUCKING MUSCIDS 227 

insectary, — temperature ranging from 23° to 26° C. The flies were 
applied for three minutes to the belly and chest of a diseased (poliomye- 
litis) monkey and then three minutes to the belly, chest and face of a 
healthy monkey, and thus exchanged back and forth at three-minute 
intervals until all flies had had a good chance to feed daily. After the 
death of the diseased monkey the flies were fed daily on the healthy 
monkey until all the flies were dead. The results were negative. 

In the next experiment a fly filtrate, made of flies which had one 
hour previously fed on a monkey at the height of the disease, was inocu- 
lated, intracerebrally, into a healthy monkey with negative results, as 
also did a filtrate made from flies having fed four days previously. 

In the fifth experiment large numbers of flies were applied daily at 
three-minute intervals between a poliomyelitis monkey and two healthy 
monkeys and continued daily on the latter after the diseased monkey 
died. The results were negative as before. 

It was thought that possibly the results of the previous investigators 
had been due to the access of the flies to infectious material on the sur- 
faces of the diseased monkeys and about their body orifices, hence a 
parallel experiment to the one above cited was undertaken with the differ- 
ence that the abdomen and chest of the diseased monkey were painted, 
before the fly feedings, with a mixture of his saliva, his feces, and (late 
in the disease) his nasal washings in physiological salt solution. Even 
so the results were negative. Later, after the death of the diseased 
monkey, an emulsion of the highly infectious brain tissue was used in 
place of the mixture of feces, saliva and nasal secretions. The brain emul- 
sion was painted on a normal monkey after which flies were applied and 
transferred as before to two other normal monkeys, all remaining well. 
Poliomyelitis had not been produced in a well monkey by stable flies 
even when they had to drive their proboscides through a layer of highly 
infectious brain tissue in order to pierce the skin, and the same flies did 
not transmit the disease on subsequent bitings of two other monkeys. 

Conclusions. — From the above-cited experiments the following con- 
clusions were drawn : 

1. In a series of seven experiments in which the conditions were 
varied we were unable to transmit poliomyelitis from monkey to monkey 
through the agency of the stable fly. 

2. Further experiments may reveal conditions under which the stable 
fly 'can readily transfer poliomyelitis, but the negative results of our work 
and of the second set of experiments of Anderson and Frost x lead us to 
doubt that the fly is the usual agent in spreading the disease in nature. 

3. On the basis of the evidence now at hand we should continue to 
isolate persons sick with poliomyelitis or convalescent, and we should 

1 Anderson, John F., and Frost, W. H., 1913. Poliomyelitis : Further 
attempts to transmit the disease through the agency of the stable fly (Stomoxys 
calcitrans). U. S. Pub. Health Reports. Washington, May 2, 1913, Vol. 
XXVIII, pp. 833-837. 

Q 



228 MEDICAL AND VETERINARY ENTOMOLOGY 

attempt to limit the formation of human carriers and to detect and 
control them. Screening of sick rooms against the stable fly and other 
flying insects is a precaution which should be added to those directed 
against contact infection, but not substituted for them. 

4. The measures used in suppressing the house fly are not appli- 
cable to the control of the stable fly owing to its different breeding habits 
and food supply. 

Control. — The more important breeding places of the Stomoxys 
can be destroyed by removing the moist feed wastes from feeding 
troughs and from stalls, stables, etc., and scattering this material so 
that it dries out quickly. Considerable moisture is necessary for the 
development of the larvae, therefore dry material is not suitable. 
Weeds, lawn cuttings, vegetables, rubbish, decaying onions, etc., 
must not be permitted to accumulate in piles long enough to decay 
and accumulate moisture. The absence of stables does not insure 
against the Stomoxys fly even though it is called the stable fly. The 
commonest fly around stables is the house fly, while the Stomoxys may be 
entirely absent. This fly is near stables because of the blood of horses, 
cattle, etc., and not because suitable breeding material is commonly 
found there. Open country without stables is sometimes over ridden 
with these biting flies. 

Bishopp (loc. tit.) has shown that straw stacks (oats and wheat) 
are important breeding places of the Stomoxys fly, hence he recommends 
" that the straw for feeding and bedding purposes be baled and stored 
under cover. Where this is not practicable the stacks should be rounded 
up so as to make the top largely rain proof and the sides nearly vertical." 

Repellent decoctions on domesticated animals only give temporary 
relief. Bishopp recommends as the most efficacious " a mixture of 
fish oil, oil of tar, and oil of pennyroyal with a little kerosene added." 

Screening barns is recommended where flies are abundant. 

Systematic. — The genus Stomoxys includes about ten species, of 
which St. calcitrans Linn, is the type, also the best known and most 
widely distributed species, occurring commonly on every continent. 

Other species, all occurring in smaller numbers in restricted localities 
in Africa, are : St. glauca Grtinb. ; St. inornata Griinb. and St. nigra 
Macquart, which is said also to occur in the Philippines, but is consid- 
ered a doubtful species by Gninberg. 



C. The Horn Fly 

Family Muscidw, Genus Hamiatobia 

Introduction. — Hcematobia serrata R. Desv. (=Lyperosia irritans L.) 
is commonly called the horn fly, also known as the Texas fly. The 
former name is applied because this fly has the habit of clustering, 
often in great numbers, at the base of the horns of cattle. Though 



BLOOD-SUCKING MUSCIDS 



229 



many believe the fly to injure the horn, there is no foundation for this 
belief. The position is probably only sought because it affords a safe 
resting place, especially at night. 

As a cattle pest the horn fly has few if any equals ; indeed, in the San 
Joaquin Valley (California) this fly is regarded as the most serious 
pest. The horn fly is a comparatively recent introduction into the 
United States from Europe, where it has been an important cattle pest 
for many years. According to the U. S. Bureau of Entomology it was 
first reported in the fall of 1887 from Camden, N. J. appearing during 
the following year in Maryland and Virginia, probably having appeared 
in Philadelphia in 1886 and by 1892 was found over the entire continent 
from Canada to Texas and from Massachusetts to the Rocky Moun- 
tains. California cattle men state that it made its appearance in this 
state in about 1893-1894. It appeared in Honolulu, Hawaii, in 1897. 

Characteristics. — The horn fly is about half the size of the common 
house fly, i.e. about 4 mm. long. It has much the same color and in 
most other respects resembles the Stomoxys fly. 
The mouth parts (Fig. 147) are as in Stomoxys 
except that the labium is relatively heavier and 
the palpi are almost as long as the proboscis, are 
flattened and loosely ensheath the same. The 
arista is plumose dorsally. The wing venation is 
as in Stomoxys. 

These flies appear early in spring and become 
most abundant in late summer and autumn. 
Both cattle and horses are attacked, but most 
especially the former. When at rest on the 
animal or elsewhere the wings lie flat on the back 
and fold rather closely, but when the fly bites, the ^ IG 147 _ side view 
wings are spread and the insect stands perpen- head of the hornfly, 
dicularly, almost hidden between the hairs ol the 
host. Apparently the habit of resting at the base of the horns is only 
developed when flies are overabundant. * 

Life History. — The horn fly deposits its eggs chiefly, if not exclu- 
sively, on freshly passed cow manure. The fly is seen to dart from the 
animal and deposit its eggs in groups of four to seven, or singly, on the 
surface of the dung. The eggs are relatively large (1.3 to 1.5 mm.), 
larger than the eggs of Stomoxys, they are reddish brown in color, hence 
not easily seen on the cow dung. Under laboratory conditions, at least, 
few eggs are deposited by the females, — rarely over twenty. At a 
temperature of 24° to 26° C. the eggs hatch in twenty-four hours. 

The larva? burrow beneath the surface of the droppings, reaching full 
growth in from three to five days when they crawl underneath into drier 
parts and pupate. The pupal period requires from six to eight days. 
Hence the entire life history (Fig. 148) from the egg to the adult requires 
from ten to fourteen days at a temperature of from 24° to 26° C. 




230 MEDICAL AND VETERINARY ENTOMOLOGY 

Damage Done. — The damage occasioned by the horn fly is chiefly 
through irritation and annoyance which results in improper digestion 
and disturbed feeding, thus producing loss of flesh and reduction of milk 
in dairy animals. Dr. James Fletcher estimated the loss in Ontario 
and Quebec at one half of the product of meat and milk. Range ani- 
mals literally run themselves thin in trying to get away from these pests. 

The actual loss of blood must be considerable when literally thou- 
sands of these flies attack an animal. The weakened condition thus 
produced lays the animal liable to disease. From ten to twenty-five 
minutes are required for the fly to fully engorge itself; during this 
time the fly withdraws and reinserts its proboscis in the same puncture 
many times as in a pumping motion. Much undigested blood is dis- 
charged from the anus of the fly while in the act of feeding. 




Fig. 148. — Life history of the "horn fly," Hcematobia serrata. x 4. 

Finally, though not absolutely proved, except through inference, the 
horn fly must certainly have the power of transmitting infectious blood 
diseases, such as anthrax. This problem has as yet not been touched 
by investigators. 

Control. — The most effective method to prevent the multiplication 
of the horn fly is to scatter the droppings from cattle with a rake or 
other implement or simply by dragging a dry branch over the field. 
Hogs allowed to run with the cattle serve this purpose very well. The 
manure thus scattered dries out quickly and the larvse if present perish 
owing to the fact that they require much moisture for development. 
The writer has seen this method applied most successfully in various 
parts of California where the dry summer favors this mode of hand- 
ling the fly. On wide ranges this method is impracticable, but in 
connection with dairies it is entirely feasible. Piles of cow manure re- 
moved from stables afford a good breeding place for the Stomoxys fly, 
especially when straw predominates, but the horn fly is not favored 
in this way to any great extent. The manure should either be stored 
temporarily in fly-tight bins like horse manure, or spread on the field 



BLOOD-SUCKING MUSCIDS 231 

at once, or else placed in containers with water to liquefy the manure, 
the containers to be covered. 

Animal sprays used as repellents are of various kinds and of various 
efficiencies. Few sprays remain effective for longer than a day or so. 
Almost any oily, greasy substance is useful, but animals thus treated in 
the presence of dusty roads and pasture become very filthy in a short 
time. The usual ingredient in sprays for this purpose is fish oil or 
train oil, though petroleum sprays are also commonly used. The latter 
are not to be recommended for use on very hot days. 

Petroleum sprays are used in the form of kerosene emulsion (crude 
petroleum, 2 gallons, \ pound soft soap, 1 gallon soft water) one part to 
five parts of water. The Kansas Experiment Station (Press Bulletin 
No. 65) recommends the following mixture as both cheap and efficient ; 
resin (pulverized), 2 parts; soap shavings, 1 part; water, \ part; fish 
oil, 1 part ; oil of tar, 1 part ; kerosene, 1 part ; water, 3 parts. The 
resin, soap, fish oil and \ part water are boiled together until the resin 
is dissolved, then add the three parts of water and finally the kerosene 
and oil of tar. The mixture must be thoroughly mixed and boiled for 
fifteen minutes. The cooled mixture is then ready for use as a spray. 

The application of the spray is done by means of a knapsack spray 
pump or other hand sprayer. One application seldom remains effective 
longer than three days, usually only a few hours. The addition of crude 
carbolic acid and sulphur is strongly recommended. 

Washburn * states that " very fine tobacco dust sifted into the hair 
on the backs and where it will find lodgment, and the above wash (a 
mixture of fish oil and crude carbolic acid) applied to other parts which 
will not hold the dust, will obtain good results." 

Smaller herds can be treated with ease by driving the animals through 
a narrow passageway, applying the spray as they pass between. On a 
larger scale it has been shown that dipping vat methods can be satis- 
factorily applied. The following is quoted from Circular No. 115, U. S. 
Department of Agriculture, Bureau of Entomology : " During the last 
three years, Mr. J. D. Mitchell, an agent of the Bureau, working with 
Mr. W. D. Hunter in Texas, has, in a study of the requirements for 
horn fly control, found that by a very simple modification of the ordinary 
dipping vat a very large percentage of the flies on cattle can be destroyed, 
with the consequent very notable limiting of the loss from the fly pest. 
With the vats as ordinarily constructed, most of the flies abandon the 
animal at the moment it plunges into the vat and escape, and go to other 
animals, and ultimately with the drying of the dipped animal return to 
it. Mr. Mitchell found, however, that by putting a splash board near 
the top of the vat on either side, about four feet above the level of the 
dip, the water thrown up violently as the animal plunges in, is caught by 

1 Washburn, F. L., 1905. Diptera of Minnesota : two-winged flies affect- 
ing the farm, garden, stock and household. Univ. of Minnesota Agr. Exp. 
Sta., Bull. No. 93. 



232 MEDICAL AND VETERINARY ENTOMOLOGY 

these splash-boards and is thrown back as a spray, filling the air space 
above the animal and drenching and destroying the flies in their effort 
to escape. The few of the horn flies that may escape, together with 
those which abandoned the animal at the entrance to the vat, were 
observed to hover or settle on the chute fence, and many would alight 
on the next animal coming along. He also found that where the ani- 
mals have been heated in corralling and getting them into the chute the 
flies stick much closer and are much less apt to take quick flight, thus 
insuring the capture of a larger percentage of them by the dip and 
spray." An oily dip must, of course, be used for this purpose. 



CHAPTER XVI 
MYIASIS 

Flesh Flies, Botflies, Warble Flies, etc. 

Myiasis is a term referring to the presence of and resultant disturb- 
ances traceable to insect larvae, primarily Diptera, in the intestine 
(intestinal myiasis), stomach (gastric myiasis), subcutaneous tissue 
(dermal or cutaneous myiasis), muscles (muscular myiasis), frontal si- 
nuses (nasal myiasis), or ears (auricular myiasis) of vertebrate animals. 
The responsible insects may relate to myiasis in a more or less accidental 
manner, as is the case with certain root maggot flies, or they may be ob- 
ligatory parasites, as is true of the bot and warble flies. 

Dipterous Larvae. — The larvae of Dipterous insects are footless and 
are commonly called maggots. Owing to the environmental setting of 
the parasitic species they may be mistaken for " worms " and are com- 
monly so designated. Owing to differences in prophylactic measures 
insect larvae and helminths should be carefully distinguished. The 
dipterous larvae are as a rule short and plump, measuring from 5 to 35 
mm. in length (less in very young larvae), and from 1 to 12 mm. in 
diameter ; they are more or less cylindrical and tapering in form ; are 
distinctly segmented, with ordinarily 11 or 12 visible segments (Fig. 
13). All insect larvae (as well as adults) possess an internal system of 
tracheated tubules, the respiratory system, which worms do not possess, 
hence with even a very minute portion of the parasite at hand, one can 
readily determine whether the specimen is insectan or not. 

All nematode worms with which maggots might most easily be 
confused are non-segmented. Annelids with which insect larvae might 
also be confused owing to their cylindrical, often plump form and 
their common segmentation, are easily distinguished from the fact that 
the former possess a larger number of segments (certainly over 20) 
and are devoid of tracheal tubules. Other important zoological char- 
acters are, of course, recognized. 

A. The Flesh Flies 

Order Diptera, Family Sarcophagida 

Adult Characteristics. — The larvae or maggots of the flesh flies are 
met with most frequently in myiasis of all forms. The adult flies are 
commonly known as blowflies. The great majority of the species de- 

233 



234 MEDICAL AND VETERINARY ENTOMOLOGY 



posit their rather conspicuous glistening white eggs on meat, dead ani- 
mals, excrement or decaying vegetable matter ; several species, notably 
the gray flesh flies (Sarcophaga) deposit living young. The blowflies 
are commonly included with the Muscidse, but by following Girschner's 
classification based on thoracic bristles all of the typical flesh-feeding 
flies are conveniently classed among the Sarcophagidse. The Sarcoph- 
agids are as a rule large flies, the smallest being about the size of the 
house fly ; the wing venation is of the Muscid type ; in color they vary 
from a bright metallic green and blue to gray; the thorax is more or 
less densely covered with bristles or heavy hairs (the Tachinid flies 
with which the Sarcophagids are most easily confused have tufts of very 
long spines on the tip of the abdomen, and the arista is bare). 

Chrysomyia (Compsomyia) macellaria Fabr. is the most important 
member of the family. 1 This fly is commonly known as the Texas 
screw worm fly, probably because the larva is pro- 
vided with intersegmentally arranged short spines 
and papillae which give it a more or less screw- 
like appearance. The fly (Fig. 149) varies in size 
from 10 to 13 mm., dependent upon the growth 
of the larva ; the ground color is a metallic green, 
with three longitudinal dark stripes on the tho- 
rax ; the head is reddish to yellowish brown ; the 
wings, when at rest are commonly folded scissors- 
like over the abdomen; the wing venation is 
similar to that of the house fly (Musca domestica) . 
The screw worm fly is typically a North and 
South American fly ranging from Patagonia to 
Canada. 

Life History. — The screw worm fly over- 
winters most commonly in the pupal stage, but, 
no doubt, also hibernates as an adult as do the bluebottle and green- 
bottle flies. Chrysomyia macellaria deposits eggs normally within its 
southern range, the time for hatching varying from less than an hour 
to twelve or more hours. But there is some difference of opinion as 
to its habits in its northern range. The writer has carried on careful 
observations on this fly during several summers along the southern 
border of Lake Erie and has never observed this fly to lay eggs. Liv- 
ing young were invariably deposited. Others (notably Hine) maintain 
that eggs are deposited. It is quite possible that the latter is true 
earlier in the summer. 

The eggs or larvse to the number of 200 to 500 are deposited on dead 
animals ordinarily, or in wounds or sores of domesticated or wild ani- 

1 For a detailed account of the ecological relationships of the Sarcophagidse 
the reader is referred to the writer's work "An ecological and experimental 
study of SarcophagidsD, etc." Journ. of Exp. Zool., Vol. 4, No. 1, pp. 45-83. 
Also "The sensory reactions of Sarcophagid flies, etc." Journ. of Exp. Zool., 
Vol. 10, No. 2, pp. 167-226. 




Fig. 149. — Chrysomyia 
macellaria, the Texas 
screw worm fly. X 3.5. 



MYIASIS 



235 



mals. Human beings are frequently attacked in the nostrils. The 
growth of the larvse is very rapid, full size being reached in three days 
under optimum conditions. The fully grown maggots vary from 12 to 
15 mm. in length ; food shortage (except when very great) as a rule only 
results in smaller larvae and smaller flies. 

When fully grown the larvse leave the carcass or wound, bury them- 
selves in loose earth or debris immediately beneath or near by, and 
enter the pupal stage in two or three days. The pupa? are chestnut- 
colored, barrel-shaped, rather rough and fairly characteristic, measuring 
from 5 to 8 mm. in 
length. Under op- 
timum conditions 
the pupal stage re- 
quires four days. 

On emergence 
from the pupal cases 
the flies crawl out 
of the sand or dirt 
and climb up near- 
by grasses, weeds or 
shrubbery, where 
the wings are spread. 
The screw worm fly 
at this time almost 
invariably turns 
about with its head 
downward after it 
has reached a rest- 
ing place. (Fig. 150.) 
Thus one often finds 
great numbers of 
flies in some re- 
stricted spot with- 
out an apparent ex- 
planation for their 
presence. The total life history of the screw worm fly from egg (or 
maggot) to imago is nine days at its shortest to two weeks and over 
under less favorable conditions. 

As Affecting Man the attacks of this fly are largely limited to in- 
dividuals suffering from nasal catarrh or unclean from vomit or with 
open sores or wounds. Sleeping individuals or persons in a drunken 
stupor are most liable to be attacked, although the fly has been known 
to dash successfully into the nostrils of wide-awake individuals, in 
which case the fly is usually not permitted to remain in the nostrils 
long enough to oviposit. Even so it is wise to properly syringe the 
nasal passages. 




Fig. 150. — Texas screw worm flies just emerged from the 
pupa cases. A dead animal near by furnished food for the 
larvae, pupation took place in the sand underneath the 
carcass. The newly emerged flies have crawled up on the 
grass and will soon be ready to fly away. Note character- 
istic resting attitude, with head down. 



236 MEDICAL AND VETERINARY ENTOMOLOGY 

The following quotation will sufficiently explain the nature of the 
injury produced. (See Osborn, 1896, pp. 127-128, quoting Richardson 
in Peoria, III. Med. Mo. for February, 1883.) 

"While traveling in Kansas in the latter part of last August, a citizen of 
this place had the misfortune to receive while asleep a deposit of eggs from this 
fly. He had been troubled for years with catarrh, hence the attraction to the 
fly. He returned home a few days after the accident and shortly after began 
complaining of a bad cold. Growing rapidly worse, I was called to attend him. 
Monday, my first day, his appearance was that of a man laboring under a 
severe cold. Had slight congestion of the lungs, and moderate fever. His 
nose seemed greatly swollen and he complained of a smarting, uneasy feeling 
in it, and general misery through the head. Gave him treatment to relieve the 
congestion and fever. Tuesday, saw him again. His nose and face were still 
swollen, and in addition to the other symptoms he was becoming slightly de- 
lirious and complained a great deal of the intense misery and annoyance in his 
nose and head. A few hours after, I was sent for in haste with the word that 
something was in his nose. I found on examination a mass of the larvae of this 
fly (or 'screw worms' as they are commonly called in the South) completely 
blocking up one nostril. On touching them they would instantly retreat en 
masse up the nostril. Making a 20 per cent solution of chloroform in sweet milk 
I made a few injections up both nostrils, which immediately brought away a 
large number, so that in a few hours I had taken away some 125 of them. By 
Wednesday evening erysipelas had begun, implicating the nose and neighboring 
portions of the face. Another physician was caUed. By continual syringing 
with a strong antiseptic solution of salicylate of soda, bicarbonate of soda, and 
carbolic acid we hoped to drown out the remaining larvae. But they had by 
this time cut their way into so many recesses of the nose and were so firmly at- 
tached that we were unable to accomplish much. Finally we resorted to the 
chloroform injections, which immediately brought away a considerable number. 
Friday I was able to open up two or three canals that they had cut, extracting 
several more that had literally packed themselves, one after another, in these 
fistulous channels. His speech becoming suddenly much worse, I examined the 
interior of his mouth and found that a clear-cut opening had been made entirely 
through the soft palate into his mouth and large enough to insert the end of a 
common lead pencil. Saturday the few remaining larvae began changing color 
and one bj r one dropped away. On Sunday for the first time hemorrhage from 
both nostrils took place, which continued at intervals for three days, but was 
not at any time severe. On this day the patient began to improve, the delirium 
and erysipelas having subsided, leaving but little or no annoyance in his head. 
In a few daj^s he became able to go about home, and even to walk a distance 
of half a mile to visit a friend and return. But while there he began complain- 
ing of a pain in the neighborhood of his left ear, apparently where the eustachian 
tube connects with the middle ear. It proved to be an abscess. Being already 
so reduced by the first attack he was unable to withstand the second, and died 
after an illness of nearly three weeks, completely exhausted by his prolonged 
sufferings. Three days before his death the abscess discharged its contents by 
the left nostril. The quantity of pus formed was about 2\ ounces (78 grams). 

"In all about 250 larvae were taken away from him during the first attack, 
and, as the visible results, not only had they cut the hole through the soft palate, 
but had also eaten the cartilage of the septum of the nose so nearly through as 
to give him the appearance of having a broken nose. The case occupied, from 
the first invasion of the fly to its final result, nearly two months. He doubtless 
would have recovered but for the formation of the abscess, which, from all the 
symptoms, was caused by one or more of the larvae having found their way up 
the left eustachian tube." 



MYIASIS 237 

As Affecting Domesticated Animals. — According to Osborn 1 cattle 
suffer most from the ravages of screw worms, in which they occur in 
wounds from horns, castrating, spraying, branding, dehorning, barbed 
wire injuries, and often where ticks have burst on the brisket, flank or 
just behind the udder of cows. They often occur in the vulvae of fresh 
cows, especially if there has been a retention of the placenta or after- 
birth. Young calves are almost invariably affected in the navel, and 
often in the mouth, causing the teeth to fall out. 

Horses and mules are not so often attacked, and if so, the maggots 
are usually found in barbed wire injuries, and occasionally in the sheaths 
of horses and the vaginae of mares and the navels of colts. 

Hogs on the other hand are more liable to become affected than horses, 
since they are frequently wounded by dogs and by fighting or there may 
be barbed wire injuries, wounds from castration, etc. 

" Sheep are attacked when injured by dogs ; or when the sheep are 
in poor condition the eggs are laid upon the wool, and when the larvae 
hatch they immediately bore into the skin. In many cases the sheep 
are attacked within the nasal cavities and the worms eat into the head." 
The reader is warned against confusing these maggots with the true 
head maggot (CEstrus ovis) . 

Other Flesh Flies. — The larvae of several species of flesh flies are 
frequently met with in gastric and intestinal myiasis. This is accounted 
for by the presence of very young maggots in meats which are eaten cold 
and not carefully masticated. Nausea and gastric disturbances may be 
traceable to this form of accidental myiasis. Owing to the small 
amount of oxygen available the growth of the larvae must needs be very 
slow. Larvae brought to the attention of the writer have been seldom 
more than 4 or 5 mm. long. 

The flesh flies deposit their eggs commonly on cold meat, particularly 
pork, if exposed to flies. The eggs hatch in from eight to twenty- 
four hours under summer conditions and the larvae grow rapidly. 

The larvae of these several species also occur frequently in wounds 
in domesticated animals and man, producing injury similar to that of 
the screw worm. 

The larvae of the blowfly or bluebottle, Calliphora vomitoria Linn, 
and C. erythrocephala, Mg. (Fig. 117^) are most commonly met with. 
The two species of flies are not usually differentiated, the two names 
being applied indiscriminately. C. vomitoria, however, has black genae 
with golden red hairs, while C. erythrocephala has fulvous genae with 
black hairs. The eggs of these species hatch in from six to forty-eight 
hours, the growing larvae feed on the flesh for from three to nine days, 
after which the fully grown larvae leave the food and bury themselves 
in loose earth. This period (prepupal period) lasts from two to seven 
days, commonly four, after which pupation takes place. The pupal 
period varies considerably according to temperature, lasting from ten 

1 Osborn, Herbert, 1896 {loc. cit.). 



238 MEDICAL AND VETERINARY ENTOMOLOGY 



to seventeen days, commonly eleven days. Thus the life history of the 
blow fly requires from sixteen to thirty-five days, commonly twenty-two 
days. The life of the adult is about thirty-five days on an average. 3 

Lucilia ccesar Linn. (Fig. 117 d), the greenbottle fly, is not so commonly 
found indoors and is typically a scavenger fly. The life history of this 
species is somewhat shorter than that of the bluebottle. The egg stage 
requires from six to forty-eight hours ; the growing (feeding) larval stage 
requires from three to seven days, commonly five days ; the prepupal 
period, commonly six days ; and the pupal period from eight to thirty- 
four days, commonly twelve days, giving a total of from sixteen to 
sixty days and over, commonly twenty-four days. Under optimum 
conditions this fly invariably requires fifteen days for its metamorphosis ; 
the average longevity of the fly is about thirty days. 

Lucilia sericata, Mg. is popularly known as the "sheep maggot fly" 
owing to its frequent occurrence on sheep. This fly resembles Lucilia 
casar very closely, and its larvae resemble the larvae of the latter even 
more closely. The female deposits her eggs commonly in the soiled 
wool of lambs and sheep. Animals suffering from diarrhea are particu- 
larly subject to attack. The newly hatched larvae live either in the 
matted wool next the skin or burrow under the skin particularly at 
points that have been injured by ticks or in other ways. 

The damage done by the larvae is often quite great. The metamor- 
phosis and time requirement for the larval and pupal periods are quite 
similar to Lucilia casar and the damage done is similar 
to that of Chrysomyia macellaria. Phormia regina Meig. 

(is also an important sheep maggot fly in California. 
Sarcophaga sarracenicE Riley is a typical flesh fly, has 
the appearance of an overgrown house fly, but is lighter 
gray, has a spiny thorax, brighter reddish brown eyes 
and is viviparous. It resembles very closely the 
larger species of parasitic Tachinid flies, but has not 
the strongly developed terminal abdominal spines. The 
young are deposited on meat, or if extruded in the vicin- 
ity of meat not accessible to the fly, the larvae crawl to 
the food. The larval stage under optimum conditions 
requires about five days, and the pupal period about 
thirteen days. 

Several African species of flesh flies are commonly 
referred to in the literature on myiasis, among them 
Cordylobia anthropophaga, E. Blanch., the " tumbu fly,' 
the larvae of which burrow beneath the skin, developing there as do the 
larvae of the warble fly, Hypoderma. It is said that babies are par- 
ticularly liable to be attacked by the " tumbu fly." Austen describes 
it as being a " thickset, compactly built fly, of an average length of 

1 Herms, W. B., 1911. The photic reactions of Sarcophagid flies, etc. 
Contributions from the Zool. Lab. of the Mus. of Comp. Zool., Harvard, No. 217. 



Fig. 151. — The 
Congo floor 
maggot, Auch 
meromyia lute- 
ola. X 2.5. 




MYIASIS 239 

about 9j mm. . . . Head, body and legs straw color. . . ." Another 
species commonly found in the same locality with the above is 
Auchmeromyia luteola, Fabr. The larva is a blood-sucker and is known 
as the " Congo floor maggot. " (Fig. 151.) The two species are said 
to resemble each other closely but Graham-Smith 1 states that " the two 
species may be distinguished by the fact that in A. luteola the eyes are 
wide apart in both sexes, the body is narrower and more elongate, the 
hypopygidium of the male is in the form of a conspicuous, forwardly 
directed hook, for which the ventral half of the penultimate segment of 
the abdomen serves as a sheath ; and lastly, by the fact that the second 
abdominal segment in the female is twice the length of the same segment 
in the male. . . ." 



"The full-grown larva is a fat, yellowish white maggot. 12 to 12^ mm. in 
length, bluntly pointed at the anterior or cephalic extremity, and truncate be- 
hind ; its greatest breadth (on the sixth and seventh segments) is 5 mm. The 
body consists of twelve visible segments, the divisions between which are strongly 
marked, except between the cephalic and first body segment (the latter of which 
bears the anterior or prothoracic stigmata, or respiratory apertures), and be- 
tween the eleventh and twelfth segments. On the underside of the cephalic 
segment the tips of the black paired mouth hooks may be seen protruding, while 
in a slight depression in the flattened posterior surface of the twelfth segment 
are situated the paired posterior stigmatic plates. In the adult larva the slit- 
like apertures in these plates are not very easy to distinguish, but in a maggot 
in the second or penultimate stage, it is seen that each plate bears three ridges 
of tawny colored chitin ; these ridges run obliquely downwards and outwards, 
at an angle of 45° from the median line, and, while the median ridge on each 
plate is nearly straight, the other two ridges are characteristically curved, re- 
sembling inverted notes of interrogation, with the concavity directed towards 
the median ridge. The segments of the body are transversely wrinkled on the 
dorsal and ventral surfaces (especially on the latter), and puckered on the sides. 
From the third to the eleventh segment the body is thickly covered with minute 
recurved spines of brownish chitin (darker in the case of larva? ready to leave the 
host), usually arranged in transverse series or groups of two or more, which 
can be seen to form more or less distinct, undulating or irregular, transverse 
rows. These spines will be described in somewhat greater detail below. 

" Above and to the outer side of each mouth hook is an antenna-like pro- 
tuberance, which, as in the case of the larva of the blowfly (Calliphora erythro- 
cephala Mg.), exhibits a pair of light brown, ocellus-like spots, or rather papilla?, 
placed one above the other. In a small larva, 5 mm. in length, from Lagos, the 
papilla? are very clearly visible ; each papilla is surrounded by a ring of pale 
brownish chitin, and its shape, when viewed from the side, is exactly that of a 
muzzle of an old-fashioned muzzle-loading cannon. 

"This small larva also shows on the basal segment of each antenna, or an- 
tenna-like protuberance, below and a little to the outer side of the mouth hook, 
a prominence bearing a series of about six small, brown tipped, chitinous spines. 
In the same larva the spines on the body are most conspicuous, and most strongly 
developed and chitinized, on the fifth, sixth and seventh segments. The tenth 
and eleventh segments are also covered with spines, but, since the chitin of 
which they are composed is not tinged with brown, these segments appear bare. 

1 Graham-Smith, G. S., 1913. Flies in relation to disease, — non-blood- 
sucking flies. Cambridge University Press, xiv + 292 pp. 



240 MEDICAL AND VETERINARY ENTOMOLOGY 

In the adult larva also, the spines of the tenth and eleventh are less conspicuous 
than those on the preceding segments; on the twelfth segment, which bears 
the posterior stigmatic plates, the spines are very minute. Fully chitinized 
spines are dark brown, but this color is generally confined to the apical half 
of the spine, or may be absent from the extreme base. In shape each spine 
is a short cone, with the apex recurved, pointing towards the hinder part of the 
body. The spines are broad at the base in proportion to their length, and not 
infrequently, especially on the under side of the body, are bifid at the tip. They 
are closest together and most strongly developed on the anterior portion of 
each segment, becoming smaller and snowing a tendency to disappear towards 
the hind margin. They are arranged in irregular transverse rows, which are 
usually seen to be composed of from two to five spines, placed side by side. 

"In the adult larva the median area of the ventral surface of the segments 
five (or six) to eleven inclusive is marked with a series of three transverse ridges, 
which are most prominently developed on the seventh and following segments. 
On each segment the foremost ridge is the shortest ; next in length comes the 
hindmost, and the middle ridge is the longest of the three, curling round the 
posterior ridge at each end. Similar but less strongly marked ridges are seen 
on the dorsal surface. 

" Pwparium. Of the usual barrel-shaped Muscid type. Average dimensions : 
length 10^, greatest breadth, 4f mm. Though at first of a ferruginous or 
light chestnut tint, the puparium gradually darkens until it becomes 'seal- 
brown' or practically black." 

Manson (loc. cit.) states that the fly deposits its eggs in the dust- 
filled cracks and crevices of the mud floors of native huts, particularly 
in spots where urine is voided. The duration of the larval life has not 
been determined. The larvae suck blood mainly at night. The pupal 
stage is said to require from two to three weeks. 

Treatment for Nasal Myiasis in Humans. — Treatment for maggots 
in the frontal sinuses and other cavities must be given without delay, 
owing to the rapid growth of the maggots and their terrible destructive 
work. Injection of a myiacide is necessary. Some of the more useful 
remedies are " 20 per cent solution of chloroform in sweet milk, a few 
injections up both nostrils," repeat until larvae are expelled ; or carbolic 
acid 2 per cent ; or infusion of pyrethrum ; or turpentine. A saturated 
solution of common salt will cause only a portion of the larvse to be ex- 
pelled but is not to be disregarded in the absence of more useful remedies, 
until a physician arrives. 

Treatment for Animals. — After locating the point of infestation, 
indicated by purulent sores, or small eaten openings, surrounded by ele- 
vations which shift or disperse suddenly when touched, the expulsion 
of the maggots, must be brought about by the introduction of an insecti- 
cide. Ordinarily a weak solution of carbolic acid (lj to 2 per cent), 
pyrethrum infusion, chloroform, creolin or chloronaphtholeum is injected. 
This may be done as recommended by Francis by means of a machinist's 
oiling can. The larvae must then be carefully scraped out and the wound 
dressed with pine tar or other curative agent. Pine tar will also act as 
a repellent against further attack by flies. 

Preventive Measures. — To prevent immediate attack by flies, 



MYIASIS 241 

animals should be carefully examined for open wounds, wire fence 
cuts, etc., so as to apply treatment and repellents to prevent the deposi- 
tion of eggs. 

Inasmuch as the flies involved in myiasis breed very abundantly 
in dead animals, all carcasses should be burned without delay or buried 
deeply and the body liberally covered with " chloride of lime." Burning 
is preferable by far. Superficially buried carcasses are easily reached by 
the young maggots hatching from eggs deposited on the ground above 
the body. Proper and expeditious disposal of all dead bodies, such as 
rats, cats, dogs, or larger animals, also of slaughter house refuse, kitchen 
garbage, manures, etc., will certainly reduce the myriads of flies which 
are a menace to the health and well-being of both man and beast on the 
farm. 

B. Anthomytjd Flies 

Order Diptera, Family Anthomyidoe 

Characteristics. — The Anthomyid flies (Fig. 117c) are usually 
grayish in color, non-metallic resembling the house fly. The first 
posterior cell of the wings is broadly open. The mouth parts are of 
the house fly type. The larvae are often vegetable feeders, either in 
living roots or in decaying vegetation, also in manures. The meta- 
morphosis is complex as in the house fly. 

Because the maggots of the Anthomyid flies are commonly found in 
onions, radishes, turnips and other roots and vegetation, their relation 
to human myiasis is easily understood, particularly when the vegetable 
is eaten uncooked. Several species of Anthomyid larvae have been 
recovered in human cases, notably Fannia (Homalomyia) canicularis, 
F. scalaris, Anthomyia radicum. 

Fannia (Homalomyia) canicularis L., commonly known as the lesser 
house fly, is frequently seen hovering in mid-air or flying hither and 
thither in the middle of the room. Where the common house fly is en- 
countered most abundantly in the kitchen or dining room, particularly 
on food, the ''little house fly" will be seen as commonly in one room as 
another, and very seldom actually on the " spread" table. The writer 
commonly observes a half dozen or more of these little flies dancing 
weirdly in the center of the lecture room midway between the floor 
and the ceiling. Various observers have estimated that this species 
constitutes from one to 25 per cent of the total population of flies in the 
house. 

In size the species varies from 5 to 6 mm. Its color is grayish, re- 
sembling the house fly very closely. Hewitt describes the male, viz., 
" Head iridescent black, silvery white, especially around the eyes. The 
antennae are blackish gray with non-setose arista. Palps black. The 
thorax is blackish gray with three indistinct black longitudinal stripes ; 
the scutellum is gray and bears long setae ; the sides of the thorax are 



242 MEDICAL AND VETERINARY ENTOMOLOGY 



lighter. . . . The legs are black and the middle femora bear comb- 
like setae below. The somewhat large squamae at the bases of the wings 
are white and the hal teres are yellow. . . . The head of the female is 
gray with a wide frons, black frontal stripe and gray sides. The longi- 
tudinal stripes of the thorax are faint and the abdomen, which is more 
pyriform than that of the male, has a slightly golden attachment/ ' 

The eggs of this species are deposited on decaying vegetable matter 
and excrement, particularly of humans, horses and cows. The larvae 
emerge in about 24 hours and may be recognized as compressed, spiny 
organisms about 6 mm. long when full grown (Fig. 152a). The pupal 
period lasts about seven days under favorable conditions. 

Fannia (Homalomyia) scalaris Fab., the latrine fly, is very similar 
to the foregoing. In size the two flies are about the same, if anything the 
latrine fly is somewhat the larger. The thorax and abdomen are bluish 
black, the antennae and palpi are black as are the legs. The abdomen 
has a dark median stripe which, with segmentally arranged transverse 
bands produces a series of dorsal triangular markings. The middle tibia 
is provided with a distinct tubercle. 

The eggs of this fly are deposited on excrement of humans, horses, 
cows, etc., also on decaying vegetable matter. The egg stage lasts 

about twenty-four hours, the larval 
stage about six days and over, and 
the pupal stage about nine days. 

While the larva of the " latrine 
fly " resembles the larva of the lesser 
house fly in general, it is readily dis- 
tinguished. The single lateral pro- 
tuberances are distinctly feathered 
(Fig. 1526). 

Anthomyia radicum Linn, the root 
maggot fly of Europe, is described 
by Meade, according to Slingerland l 
viz. : "It may be recognized by its 
projecting face ; by the scales of the 
base of the wings being unequal in 
size ; by the thorax being black and 
marked in the male by two short, 
gray, narrow stripes ; by the rather 
short, wide, somewhat pointed 
abdomen, with a longitudinal dorsal black mark, crossed by three 
transverse straight black stripes extending of an equal width to the 
margins ; and by the third and fourth longitudinal veins of the wings 
being slightly convergent at their extremities. This inequality in the 




Fig. 152. — (a) Larva of Fannia {Ho- 
malomyia) canicularis; (6) Larva of 
Fannia {Homalomyia) scalaris. (Re- 
drawn and adapted after Hewitt.) X 6. 



1 Slingerland, M. V., 1894. The cabbage root maggot, with notes on the 
onion maggot and allied insects. Cornell University Agr. Exp. Sta., Bull. 
No. 78, pp. 481-577. 



MYIASIS 243 

size of the alular scales, the shape of the abdomen, the markings on 
the body, and the convergence of the third and fourth longitudinal 
veins of the wings are characters, any one of which would distinguish 
the male fly, at least, from the cabbage fly " (Phorbia brassicce, Bouche). 

Anthomyia radicum is a typical root maggot fly, its larvae developing 
in the roots of radishes and other plants ; Bouche records the maggots 
as developing in human excrement. According to Slingerland (loc. 
cit) this author gives eight to ten days as the period required to 
pass through the egg and larval stage and two or three weeks for the 
pupal stage. Hewitt (loc. cit.) gives the egg stage at from eighteen to 
thirty-six hours, the larval stage at about eight days and the pupal 
stage about ten days. 

The fully grown larva measures " 8 mm. in length and may be dis- 
tinguished by the six pairs of spinous tubercles surrounding the posterior 
end and a seventh pair situated on the ventral surface posterior to the 
anus. The tubercles of the sixth pair, counting from the dorsal side, 
are smaller than the rest and are bifid " (Hewitt). The ingestion of 
the larva with uncooked vegetables not thoroughly masticated, seems 
to be the mode of infection. 

Relation to Gastric and Intestinal Myiasis. — Many cases of intesti- 
nal myiasis traceable to Anthomyid flies are recorded. (See Parasitology, 
Vol. 5, No. 3, pp. 161-174.) " The presence of these larvae in the stomach 
is usually indicated by nausea, vertigo and violent pains ; the larvae 
in many cases are expelled by vomiting. If they occur in the intestine, 
they are expelled with the feces and their presence is signalized by diar- 
rheal symptoms, abdominal pains or haemorrhage caused by the trau- 
matic lesions of the mucous membrane of the intestine which the larvae 
affect" (Hewitt). 

Mode of Infection. — As has already been explained, the eggs of these 
flies may be deposited upon] decaying or even fresh vegetable matter 
or excrement, in which the larvae develop. It seems quite probable that 
the young larvae (possibly also the eggs) are taken into the stomach in 
uncooked food. It is also suggested (Hewitt) that the flies may deposit 
their eggs in or near the anus, particularly in the use of old-fashioned 
open privies. The larvae on hatching are believed to make their way into 
the intestine. 

Larvae in the Urinary Tract. — Infestation of the urinary tract by 
larvae of Fannia canicularis is by no means uncommon according to 
Chevril. 1 The expulsion of larvae with the urine in both sexes has been 
recorded. Entrance into the urinary tract is undoubtedly gained by 
the larvae through the genital openings (of females primarily), to which 
the adult flies have been attracted by secretions on exposure of these 
parts during sleep or drunken stupor. 

1 Chevril, R., 1909. Sur la myase des voies urinairei. Arch, de Parasitol., 
XII, pp. 369-450. 



244 MEDICAL AND VETERINARY ENTOMOLOGY 



C. Rat-tailed Larvae 

Order Diptera, Family Syrphidw 

Characteristics. — The family Syrphidae includes a very large group 
of flies, many of which are brightly colored, varying greatly in size. 
They are nearly all flower loving, feeding on nectar mainly. Only 
one genus needs be considered here, namely, Eristalis, the' larvae of which 
have a long anal breathing tube, i.e. <( rat-tailed," and the adults are 
commonly called drone flies. 

Eristalis tenax, the drone fly (Fig. 153), is a rather large insect, 
somewhat larger than a honeybee and resembles the drone bee very 

closely, indeed is commonly 
referred to as its mimic. The 
fly deposits its eggs on liquid 
manure or other filthy liquids 
in cans, slop jars, privies, etc. 
The larvae are known as " rat- 
tailed larvae" (Fig. 154); 
these also occur occasionally 
in heaps of horse manure. 

Relation to Myiasis. — The 
frequency with which the " rat- 
tailed " larvae occur in liquid 
excrement must lead to ex- 
treme caution in accepting re- 
ports that these larvae have 
been evacuated with discharges 
from the bowels. The writer 
has on several occasions re- 
ceived specimens of " rat- 
tailed ' ' larvae which were said 
to have been evacuated by the 
" double handful " and that 
the patient had "steadily improved" thereafter. 

There are, however, several cases on record which seem to be in- 
controvertible, notably the case reported by Hall and Muir, 1 who also 
bring together all recorded information to date relative to Eristalis and 
myiasis. The case referred to was that of a boy aged five years 
" who had been ailing for about ten weeks and who was under medical 
treatment for indigestion and obstinate constipation for about five 
weeks of that time. The child was emaciated and anemic. Very 
striking symptoms were the constant and pronounced twitching of the 
eyelids and other nervous movements. He gritted his teeth in his 

1 Hall, M. C, and Muir, J. T., 1913. A critical study of a case of myiasis 
due to Eristalis. Archives of Intern. Med., Vol. II, pp. 193-203. 




Fig. 153. — The drone fly, Eristalis tenax, 
whose larvae are commonly called "rat- 
tailed larva?." X 3.5. 



MYIASIS 



245 



sleep at times, and made convulsive movements of the limbs. When 
awake he complained of pain in the limbs and headache. The emaci- 
ation seemed to be due to the fact that the boy had for some time 
vomited almost everything he ate. The 
breath was very bad, ' worse than rotten eggs ' 
according to his parents. On the basis of 
the nervous and digestive disturbance and 
the general debility, a diagnosis of worm in- 
festation was made." 

With this diagnosis in mind the mother 
of the boy gave him a dose of a proprietary 
worm remedy, resulting in the discharge of 
an object wriggling around vigorously in the 
feces and urine. The slop jar into which 
the stool was passed was in regular use and 
had been previously rinsed with tap water 
and allowed to dry during the day. The 
specimen was identified by the authors as one 
of the "rat-tailed larva? " measuring 3.2 cm. 
in length, including the long " tail." A 
second larva was said to have been dis- 
charged the following day. The case is be- 
lieved by the authors to be probably a 
genuine case of " gastric myiasis." 

After the passage of the larva? the child is 
said to have improved in health and became 
normal, the nervous symptoms and vomiting 
disappeared. 

Three chances for infection were pointed out ; namely, first, the eating 
of "overripe" or probably decaying peaches in which "rat-tailed" 
larvae might have occurred ; or, secondly, to the drinking of " ditch " 
water polluted with kitchen refuse, etc. ; or, lastly, to stable manure in 
a neighbor's yard where the child played. 

The authors offer the following comment relative to the gastric dis- 
turbances : 

"A larva supplied with the stigmatic apparatus of Eristalis would apparently 
be fitted for life in a stomach with a small amount of food and plenty of the 
atmospheric air which is swallowed in eating and drinking and at other times. 
Such a condition would simulate the normal life conditions fairly closely. 
That the stomach would not fill to the point where it would drown the larva 
might be insured by the vomiting, perhaps automatically, the activity of the 
larva increasing as 1he stomach filled to where it threatened to cover the rising 
stigmatic tube, and so setting up an irritation leading to vomiting. The 
mother states that the child's stomach was extremely intolerant of milk and 
that drinking milk w T as promptly followed by vomiting. This suggests that 
milk, usually taken in long drinks and considerable quantities, quickly threat- 
ened the larva with drowning and set up such activity as promptly to cause 
vomiting." 




Fig. 154. — The "rat-tailed 
larva" of Eristalis tenax, 
drone fly. X 2. 



246 MEDICAL AND VETERINARY ENTOMOLOGY 

D. Botflies 
Order Diptera, Family GEstridce 

Characteristics of the (Estridae. — The (Estridse are described by 
Williston as follows : " Flies of moderate to rather large size, thick- 
set, usually more or less pilose. Head large, the lower part more or less 
swollen. Antenna? short, three-jointed, decumbent, and more or less 
sunken in the facial groove or grooves ; arista bare or plumose. Mouth 
opening small, the mouth parts sometimes rudimentary, never large. 
Front broad in both sexes, in the male broader in front. Eyes compara- 
tively small, bare. Ocelli present. Thorax robust, with a distinct trans- 
verse suture. Abdomen short, conical or but little elongated ; genitalia of 
the male hidden, the ovipositor sometimes elongated. Legs moderately 
long, the hind pair sometimes elongated. Tegulse usually large ; some- 
times small. Neuration of the wings muscid-like, in most cases the 
first posterior cell narrowed or closed ; anal cell small, usually indistinct ; 
discal cell sometimes absent. 

" This family, though of small size comparatively, is of the greatest 
interest by reason of the habits of the larvae, all of which that are known 
are parasitic upon mammals. The adult flies often have rudimentary 
mouth parts, and devote the whole of their brief existence to the labors 
of procreation. . . . Parasitism occurs in three principal ways, in the 
stomach and digestive tubes, in tumors formed by the larvae under the 
skin and in the pharyngeal and nasal cavities. With but few excep- 
tions each species is confined to a single species of mammal, and each 
genus or each group of allied species is parasitic in the same way upon 
similar animals." 

a. Horse Bots 

Characteristics. — Gastrophilus equi Fabr. is the common horse bot 
(Fi^. 155). This species is described by Osborn, viz., " Adults of this 




Fig. 155. — The horse botfly, Gastrophilus equi. (Female, left ; male, right.) X 1.6. 

species are about 18 mm. in length, the wings are transparent with 
dark spots, those near the center forming an irregular transverse 



MYIASIS 



247 




Fig. 156. — Eggs 
of the horse bot- 
fly, attached to 
a hair of the 
host. X 20. 



band. The body is very hairy, the head brown with whitish front, 
thorax brown, abdomen brown with three rows of blackish spots, 
which are subject to considerable variations. In the 
females the segments are often almost entirely brown 
with simply a marginal series of yellowish spots, while 
in the males the abdomen may be almost entirely yellow 
or very light brown, with brown or dark brown spots 
very distinct. The males are rarely seen, for while 
it is one of the most common occurrences to witness 
the females around the horses depositing their eggs, 
the males evidently hold aloof. They are readily dis- 
tinguished by the form of the abdomen, which lacks 
the two tubular segments at the end, and is provided 
on the under side of the last segment with a pair of 
dark brown or black hooks, or clasping organs. Other- 
wise, except the color of the abdomen, already men- 
tioned, they resemble very closely the females." 

Life History. — The eggs (Fig. 156), which are light 
yellow, are attached to the hairs of the forelegs, belly, 
shoulders and other parts of the body. The female 
fly may be seen hovering two or three feet away from 
the horse, and suddenly is seen to dart at the animal, fastening an 
egg firmly in place. This process is repeated until perhaps several 
hundred eggs may be attached. The very careful 
observations of Osborn (and corroborated in the 
main by the writer) indicate that " the eggs 
normally require friction and moisture to permit of 
their hatching and transfer to the horse's mouth, 
that hatching occurs with difficulty before the tenth 
day, and most readily after the fourteenth day, and 
that they lose vitality at a period varying between 
the twenty-eighth and fortieth days, the bulk not 
surviving- more than four weeks. " The newly 
hatched larva is a very spiny creature (Fig. 157) 
which readily adheres to moist surfaces, hence must 
easily adhere to the rough, moist tongue of the horse, 
passing into the mouth and gradually working its 
way down the esophagus to the stomach, where it 
attaches itself to the mucous lining by means of the 
strong oral hooklets. The stomach wall often be- 
comes so crowded with bots that there is hardly 
room for a finger to touch the stomach without 
coming in contact with bots (Fig. 158). 

The bots remain attached, growing slowly 
throughout the rest of the summer, autumn and winter, until late 
spring, when full growth is reached, having molted twice during this 



Fig. 157. — Newly 
emerged larva of 
the horse botfly. 
X60. 



248 MEDICAL AND VETERINARY ENTOMOLOGY 



time. They are then from 1.6-2 cm. long (Fig. 159). At this time the 
insects let go, gradually pass out through the intestine with the feces 
and drop to the ground. Reaching the ground, the bots burrow into 
loose earth and in a few days pupate. The pupal period varies con- 
siderably, depending upon moisture and temperature conditions, but the 
usual time is from three to five weeks, when the winged flies emerge. 
Copulation takes place soon, inasmuch as the insects probably partake 




Fig. 158. 



Horse bots (Gastrophilus equi) attached to inner lining of the stomach 
of a horse. (Photo by Wherry.) X .75. 



of little or no food; egg laying begins again in early summer, and as 
new individuals emerge continues until autumn. 

Pathogenesis. — While a moderate infestation of bots will give no 
outward indications, a heavy infestation will be indicated by digestive 
disorders (which may of course be traceable to other causes as well). 
The discovery of bots in the manure is sufficient evidence. A light in- 
festation is probably of no consequence, — there are indeed some indi- 
viduals who erroneously maintain that a horse must have at least a few 
bots in order to be well. 



MYIASIS 



249 




The injury which bots produce is, first, abstraction of nutriment, 
both from the stomach and its contents ; second, obstruction to the food 
passing from the stomach to the intestine, particularly when the larvae 
are in or near the pylorus ; third, irritation and injury to the mucous 
membrane of the stomach due to the penetration of the oral hooklets ; 
fourth, irritation of the intestine, rectum and anus in passage. 

Treatment. — Internal remedies are always best and most safely ad- 
ministered by a veterinarian. However, turpentine is commonly used 
in four-ounce doses, four hours apart, until three or four doses have been 
administered. It is recommended that the last dose be followed by one 
ounce of powdered aloes. The use of turpentine is dangerous unless 
it is given by an experienced person. 
Washburn 1 states that carbon bisulphide 
has been used in Italy with marked success. 
Six gelatine capsules, each containing 15 
grains of CS 2 , were given to two horses at 
intervals of two hours. During the four 
following days the first horse passed 497 bots, 
the second in five days, 571 bots. Another 
party gave one horse 32 grains in five hours, 
and the animal passed 203 bots. Horses so 
treated should be carefully watched, and if 
any bad effects appear, treatment should be 
stopped. 

Prevention. — The object in view is to 
prevent the botfly larvse from gaining en- 
trance to the mouth of the horse, hence 
control methods involve the egg. The first 
method that presents itself is to prevent the 
fly from depositing its eggs on the horse. 
This can be done by keeping the animals 
stabled during the day, giving them free 
range at night. 

A second method involves the destruction or removal of the eggs 
from the horse. Touching the eggs lightly with kerosene, benzine or 
gasoline proves effective. The eggs are easily removed with a sharp 
razor or clippers, in which case treatment is unnecessary. 

Based on our knowledge of the egg stage it would seem that very 
few bots would reach the stomach of the horse if the animal is treated 
as above at least once every two weeks. 

If internal remedies are administered and the bots are full grown 
or nearly so, it is safer to treat the manure copiously with kerosene, 
carbolic acid or sheep dip in order to destroy the larvae to prevent 
pupation and emergence of the flies. 

Other Species of Horse Bots. — Gastrophilus hcemorrhoidalis Linn, is 

1 Washburn, F. L., 1905 (loc. cit.). 









Fig. 159. — Larva of Gastro- 
philus equi, the horse bot. 
X4. 




250 MEDICAL AND VETERINARY ENTOMOLOGY 

the red-tailed bot . This species is about 1 . 5 cm . in length with an orange- 
red-tipped abdomen. " The thorax is olive-gray and hairy, with a black 
band behind the suture. The base of the abdomen is whitish and the 
middle blackish, in strange contrast with the orange-red of the end." 
The eggs of this species are dark brown to nearly black and are deposited 
on the long hairs of the horse's lip. The incubation period is very much 
shorter than in G. equi. The larvae find their way into the mouth on 
food or with the tongue in licking, and eventually reach the stomach. 
The fully grown larvae are from 12 to 15 mm. long. Law describes 
the larvae, viz. : " The spines are arranged in a double row on each ring, 
but on the dorsal aspect they are absent in the middle of the ninth ring, 
while on the tenth and eleventh there are none. The larvae pass the 
winter mostly attached in groups in the left sac of the stomach, but also 
in the right sac, and duodenum, and exceptionally in the pharynx." 

" When mature and passing out through the intestines they often 
hook themselves for a time to the rectal mucosa, where they cause con- 
siderable irritation and rubbing of the tail. They also pass through the 
anus independently of defecation, and hook themselves to the skin 
round its outer margin, causing rubbing and switching of the tail, and a 
stiff awkward gait. This habit, with that of laying the eggs on the lips 
and jaw, and of hooking on the delicate mucosae of the pharynx, right 
gastric sac and duodenum, renders this one of the most injurious of the 
(Estridae" (Osborn). 

The pupal stage is entered soon after the bot drops to the ground 
and buries itself, and lasts from four to six weeks and over. The flies 
occur from early summer to late autumn. 

Gastrophilus nasalis Linn, is the chin fly, which measures about 
1 cm. in length. It is " densely hairy, with the thorax yellowish red 
or rust colored. The abdomen is either whitish at the base, with the 
middle black and the apex yellowish brown and hairy, or the base is 
whitish and all the rest brown ; or the middle is black ; with the base 
and apex whitish, with grayish hairs. The wings are unspotted " (Ver- 
rill). 

The white eggs are deposited on the lips or around the nostrils. The 
larvae are " furnished with a row of spines on each ring from the second 
to the ninth on the dorsal surface, and as far as the tenth on the ventral. 
There is an unarmed part in the center of the eighth and ninth rings on 
the dorsal surface. It spends the winter attached to the mucosa of the 
commencement of the duodenum, usually in clusters, and is rarely found 
in the stomach. In passing out it shows no tendency to hook itself to 
other parts of the intestine or the anus " (Law). 

The remainder of the life history is as in other species already de- 
scribed. 

Gastrophilus pecorum Fabr. is about the same size as G. equi. 
In color it is yellowish brown to nearly black. The wings are brownish 
and clouded. In egg deposition, life history and habits this species re- 



MYIASIS 



251 



sembles G. equi very closely. It is said to be rare or absent in the 
United States. 

b. Ox Warbles 

Characteristics. — Hypoderma lineata Tillers is the common ox 
warble fly (Fig. 160), also known as the "heel fly," which, together 
with a less prevalent species, H. bovis De G., is responsible for the 
warble or grub in cattle. This species is described as follows : 
"Length, 13 mm. (15 mm. with ovipositor extended) ; general color, 
black; body more or less clothed with yellowish white, reddish and 
brownish black hairs. The front, sides, and back of the head, the 
sides of the thorax, a band across the base of the scutellum, and 
the basal segment of the abdomen are covered with long yellowish 
white, almost white, hairs. The head above, central thoracic region, 
including prothorax and mesothorax, middle segments of the ab- 
domen above, and legs, clothed with brownish 
black hairs, which on the head and thorax 
are more or less intermixed with whitish 
hairs. The covering of hairs is shorter and 
scantier on the head and thorax, and the tip 
of the scutellum and following parts of the 
thorax, together with four prominent lines 
on the thorax, smooth and highly polished. 
The hairs of the terminal segments of the 
abdomen are reddish orange, which color 
also predominates on the hind tibiae." 

Life History and Habits. — The female 
deposits her eggs on the feet, legs, flanks, 
belly and other parts of the body. The eggs 
are white, about 1 mm. long, and are securely 
attached in rows of six, more or less, on a 
single hair. Deposition occurs from early 
summer to late autumn. The larva? hatch 
in a week more or less, protruding the body 
from the egg or crawling out and clinging to 
the hairs of the host, when they are licked off 
with the tongue, pass into the mouth, thence into the esophagus, and 
often into the paunch. Once in the esophagus or paunch the larvae 
burrow, finding their way into the tissue between the mucous mem- 
brane and the muscular coat of these organs. In this region the 
smooth yellowish white larvae remain for the rest of the summer and 
autumn and grow to be from 12 to 15 mm. in length. During the late 
autumn and winter the still smooth larvae begin to penetrate the muscu- 
lar coat of the esophagus, entering the connective tissue of the abdominal 
cavity and dorsal muscles, continuing their migration toward the back 
of the host. The large warble ( Hypoderma bovis) is said to often enter 




Fig. 160. — The ox warble fly, 
Hypoderma lineata. X 2.6. 



252 MEDICAL AND VETERINARY ENTOMOLOGY 



the spinal canal through the intervertebral foramina, remaining there 
for two or three months and leaving this location by the same path which 
was followed on entering, and soon find their way to their ultimate posi- 
tion in the host in the subcutaneous connective tissue beneath the skin 
of the back. Larvae are also known to enter the skin directly. 

About the latter part of December (the writer has observed them 
about Christmas time) there appear the small swellings along the back 
(near the spinal column) of the cattle. These lumps it will be noted 
change in position from day to day, appearing on the shoulders, sides and 
rump as well. Soon the lumps become stationary and there appears a 
small opening in the middle of the elevated area through which the grub 
receives oxygen, having its posterior end close to this hole. The skin is 
again shed (the third and last molt) and the larva now appears as a 
thick heavy set spiny maggot about 25 cm. in length (Fig. 161). The 
tumor increases to the size of a walnut, the aperture becomes larger and 
in early to late spring the grub crawls out, falls to the ground, burrows 
into loose earth and in a day or two pupates. 
The pupa is about 2 cm. long, dark brown to 
black in color. The winged insect emerges from 
the pupa case in from three to five weeks and 
over. 

Hypoderma bovis De G. is commonly called 
the European or larger warble fly. This species 
is now known to occur in British Columbia. In 
Europe, H. Bovis predominates over H. lineata. 
It is about 15 mm. in length against 13 mm. in 
the latter. Both species are hairy, resembling 
bees, the ground color is black with long hairs 
on the front, sides and back of the head, sides 
of thorax and base of abdomen. In H. bovis 
these hairs are greenish yellow. The tip of the 
abdomen in both species is reddish yellow, 
deeper and more hairy in H. bovis. 

The life history of the two species is very 
similar. The larvae are different enough to distinguish them readily. 
The fully grown larva of H. bovis is longer, 27-28 mm., H. lineata 
about 25 mm. The two species are distinguished on the basis of their 
spiny armature. In H. lineata each segment of the larva is provided 
with spines except the last, the ring upon which the stigmata are 
located, while in H. bovis all except the last two are armored. 

Injury Done. — The injury done by the warbles is first that of irritation 
caused by their migrations in the body of the animal and later in their 
emergence from beneath the skin ; secondly, the escape of the larva from 
the tumor leaves an open, running wound which persists for a long time 
and is attractive to screw worm flies and other tormenting insects. The 
direct pathogenesis is of minor importance, however, in the face of the 
economic loss produced by this insect. 




Fig. 161. — Larva or grub 
of the ox warble fly, 
Hypoderma lineata. 
X 1.3. 






MYIASIS 



253 



Economic Losses. — The economic losses produced are first, reduc- 
tion in milk secretion, which is estimated at from 10 to 20 per cent of the 
normal yield ; second, loss of flesh due to the wild endeavor of the ani- 
mals to escape from the flies and the irritating larvae (which is pointed 
out by Holstein, viz. : " A cow quietly grazing will suddenly spring for- 
ward, throw up her tail, and make for the nearest water at a headlong 
gait. Seemingly deprived at the moment of every instinct except the 




Fig. 162. 



A piece of sole leather (Grubby Jumbo), 21 X 31.5 cm. showing work of 
ox warble. X 3. 



desire to escape, she will rush over a high bluff on the way, often being 
killed by the fall. This, with miring in water holes and the fact that 
cattle are prevented from feeding, causes the loss") ; third, depreciation 
of the value of the carcass as flesh, which becomes greenish yellow and 
jelly-like in appearance at the points where the grubs are located, and is 
not fit for consumption ; fourth, injury produced to the hide which be- 
comes ' grubby,' full of holes where the grubs have emerged (Fig. 162). 
The following is quoted from Tanners' Work for October, 1913 : 
" The case is recorded by Boas of Denmark of a cow which remained in 
poor condition and gave 33 pounds of milk per day. Forty-six grubs 
were extracted from this animal and eight days later she was giving 44 
pounds of milk per day, continued to do so most of the summer and was 
in good flesh and condition in the fall. In this case the loss of milk due 
to the grub infestation was 25 per cent. The loss in flesh on account 
of grubs has been variously estimated at from $1.00 to $5.00 or more 



254 MEDICAL AND VETERINARY ENTOMOLOGY 

per head. If we assume that 25 per cent of all of the cattle in the United 
States are more or less infested with grubs, a quite conservative estimate, 
50 per cent probably being nearer the actual percentage, the loss in flesh 
on account of grubs amounts to from 815,000,000 to $75,000,000 a year, 
the total number of cattle in the United States being calculated as ap- 
proximately 60,000,000. If we also assume that infested milch cows 
lose 10 per cent in milk production and that 25 per cent of the 20,000,000 
milch cows in the United States are affected, there should be added to the 
account a loss of not less than 830,000,000 per year. 

" As to the loss in hides it is stated byEuropean tanners that a grubby 
hide is, on the average, less in value by one third than a perfect hide, 
but for this country, I have no definite information other than that 
grubby hides in the green state are commonly valued at 1 cent a pound less 
than perfect hides. On this basis the depreciation in value of a hide of 
average weight of 65 pounds if grub-infested, would be 65 cents and the 
depreciation in the value of the estimated 15,000,000 grubby cattle of 
the United States so far as their hides are concerned thus amounts to 
89,750,000. It is, however, quite probable that the actual loss in the 
value of hides when made into leather is much greater than this. 

" Without including the loss on account of the direct damage to beef 
carcasses from the presence of grubs, we may, on the basis of the forego- 
ing, estimate the total loss from grubs in the L^nited States in round num- 
bers at from 855,000,000 to 8120,000,000 per year." 

Treatment. — The tumors in which the grubs occur may be treated 
with kerosene, benzine, turpentine or carbolic acid, a few drops of which 
are introduced into the opening by means of a machinist's oiler, or merely 
smeared over the surface. Ointment of sulphur and vaseline are also 
serviceable. These remedies are objectionable inasmuch as the grubs 
are not eliminated, dying within the tumor where they must be slowly 
absorbed ; . serious abscesses may result. 

The grubs may also be destroyed in situ with a sharp scalpel or a hot 
needle, but here again the same objection as above is encountered. 

A better method is to remove the grubs bodily, which can easily be 
done by squeezing them out if the grubs are about ready to leave the 
tumor. If not easily squeezed out, a forceps with slender blades may be 
introduced into the opening, the grub grasped and eliminated. In some 
cases the use of a lancet may be needed to widen the opening in the 
tumor. 

After removal the grubs must be destroyed to prevent further 
metamorphosis, and the wound should be treated with a carbolated 
salve. 

Prevention. — Owing to the fact that the eggs hatch very soon after 
deposition, treatment with kerosene, benzine or gasoline would have to 
be given as soon as the eggs are noticed. This treatment is not particu- 
larly practical but is not to be disregarded. 

Removal of the grubs or treatment of the same prevents the comple- 



MYIASIS 



255 



tion of metamorphosis and hence results in the reduction of the number 
of adult flies for the next season. 

Associations for the eradication of grubs have been formed in Europe, 
which cope with the problem through educational methods. In some 
districts a bounty is offered from J cent to f cent per grub. Their efforts 
have given very good results. No practical method of eradication in 
range animals is at hand, but certainly there is no reason why with proper 
cooperation and systematic effort this evil could not be controlled where 
only smaller herds are concerned, thus actually saving large sums of 
money to the stock raiser and dairyman. 



c. Head Maggot of Sheep 




Fig. 163. 



Head maggot fly (CEstrus ovis) 
of sheep. X 4. 



Characteristics. — Oestrus ovis Linn, is the botfly of sheep, or the 
sheep gadfly, the larva of which is the common head maggot of these 
animals. ' Grub-in-the-head,' 
' false gid ' and ' staggers ' are 
common designations. 

The fly (Fig. 163) is some- 
what larger than the common 
house fly, dull yellow or brown- 
ish in color and hairy. The 
abdomen is variegated with 
brown and straw yellow, the feet 
are brown. It is further de- 
scribed by Osborn as follows : 
" The under side of the head is 
puffed out and white. The 
antennae are extremely small and 
spring from two lobes which are sunk into a cavity at the anterior and 
under part of the head. The eyes are purplish brown, and three small 
eyelets are distinctly visible on the top of the head. It has no mouth 
and cannot, therefore, take any nourishment. The wings are trans- 
parent and extend beyond the body, and the winglets (calypteres) which 
are quite large and white, cover entirely the poisers. It is quite lazy, 
and, except when attempting to deposit its eggs, the wings are seldom 
used." 

Life History. — The head maggot fly deposits living young from 
early summer to autumn in the nostrils of sheep and goats. These 
at once begin to migrate up the nasal passages, working their way up 
into the nasal sinuses often as far as the base of the horns in rams 
and attach themselves to the mucous membranes. Here numbers of 
these whitish grubs may be found wedged in closely in various condi- 
tions of development (see Fig. 167). The posterior ends which are 
unattached present conspicuous spiracles. The grubs (Fig. 164) reach 



256 MEDICAL AND VETERINARY ENTOMOLOGY 

full growth with a length of from 25 to 30 mm. by the following spring, 
— a larval period of from eight to ten months. At the end of this 
time they let go, wriggling their way out of the nostrils, fall to the 
ground, bury themselves in the earth and pupate in a few hours. The 
pupal period lasts from three to six weeks and over. 

Symptoms. — In the presence of the fly the sheep are very much 
excited, shake the head, rush with their noses between their fellows, 





Fig. 164. — Head maggot 
(CEstrus ovis) of sheep. 
X2.5. 



Fig. 



165. — The larva of a rabbit botfly, 
Cuterebra sp. X 3. 



push their noses into the dust, snort and otherwise indicate that they 
are trying to escape something that persists in entering the nostrils. 
Once infected there is a purulent discharge from the nostrils, vigorous 
shaking of the head, and perhaps occasional discharge of a maggot, loss 
of appetite, grating of the teeth, and when the animal walks the fore 
feet are lifted in a pawing movement. 

The great majority of the cases do not result fatally, but death 
often results in a week more or less after the appearance of aggravated 
symptoms. 

Grub-in-the-head is distinguished from a gid" (caused by a larval 
tapeworm, Ccenurus cerebralis = Multiceps multiceps) in that the former 
is always associated with purulent discharges from the nostrils/ absent 
in the latter, and that the symptoms of the former appear during the 
summer, and that the latter occurs ordinarily in lambs and yearlings 
only ^Law). There is no undue sneezing or rubbing of the nose in gid. 



MYIASIS 257 

Treatment. — Materials such as snuff, pepper, etc., may be in- 
troduced into the nostrils or sprinkled among the flock, to induce violent 
sneezing, which causes the expulsion of many of the larger grubs. Law 
recommends the injection of benzine, lifting the sheep's nose somewhat 
and pouring into the nostrils a teaspoonful of the remedy for each 
nostril. The lower nostril into which the benzine is poured is held 
shut for thirty seconds; the other side is then turned and the treat- 
ment repeated. The application is repeated daily or oftener until the 
maggots are all expelled. 

Prevention. — The use of " salt logs " in sheep pastures is made by 
some sheep raisers. These logs are made by boring two-inch holes at 
intervals of about six inches along the length on top. Salt is placed 
into these holes, which are kept about half full, and in turn the edges 
of the holes are repeatedly smeared with pine tar, or other repellent 
material. In endeavoring to reach the salt the sheep involuntarily 
smears its nose with the substance, which protects it to a large extent 
against the head maggot fly. 



d. Bots in Rodents 

Bots in Rodents. — Various species of rodents, notably rabbits, 
rats and squirrels are infested at times with bots or perhaps we had better 
say, warbles (Fig. 165). Rabbits, both wild and tame, are commonly 
affected by Cuterebra cuniculi Clark, and 
probably other species. C. cuniculi is a 
large black and white bumblebee-like 
fly (Fig. 166). Just where the eggs are 
deposited and how the grubs reach their 
position under the skin is still unknown. 
After leaving the body of the host the 
larva? pupate in three or four days, re- 
maining in the pupal stage often for a Fig. i66. — a rabbit botfly, 

•j T-i • i i- j Cuterebra sp. X 1.3. 

considerable period; one case observed 

by the writer pupated October 25, 1912, and emerged August 12, 1913. 
The emasculating bot (Cuterebra emasculator Fitch) of squirrels is 
found in the grub stage in the scrotum of squirrels of several species. 



e. Head Maggot of Deer 

Head Maggot of Deer. — The black-tailed deer (Odocoileus colum- 
bianus) and probably other species as well are commonly affected with 
head maggots, a species of the genus Cephenomyia. The attached 
figure (Fig. 167) illustrates the fact that the larvse crowd into the si- 
nuses and that there are all sizes, from very young to fully grown, present 
at the same time. 




258 MEDICAL AND VETERINARY ENTOMOLOGY 

/. Warbles in Humans 

Warbles in Humans. — Humans, notably in Central and South 
America, Mexico and other tropical countries, are rather commonly 
affected with warbles traceable to one of several species of GEstrids, 




Fig. 167. — Head maggots, larvae of Cephenomyia sp. attached^to tissue in nasal 
sinuses of the deer. X .6. 

notably Dermatobia hominis Gmelin = Dermatobia noxialis Guodot = 
Dermatobia cyaniventris MacQ., Hypoderma lineata, Vill., and H. boms, 
DeG. 

Dermatobia hominis Gmelin l is commonly found in Central and 
South America and Mexico. The larva is known in its early stage as 
Ver macaque and in its later stages as torcel or berne. The fly measures 
from 14 to 16 mm. in length, is entirely brown in color. This fly para- 
sitizes a large number of species of mammals and even birds. It has 
been found in cattle, pigs, dogs, mules, monkeys, man and various wild 
animals. In man the larva " has been reported from various regions 
of the body, mainly head, arm, back, abdomen, scrotum, buttocks, thigh 
and axilla." 

Whether the fly introduces the egg under the skin of its host by means 
of the ovipositor is unknown but in certain recorded cases there is a his- 
tory of a sting. According to some authors the larval period requires 
about three months when the insect leaves the flesh, drops to the ground 
and pupates, the pupal period requiring about six weeks. 

Pathogenesis. — The following is quoted from Ward (loc. cit.) : 
" Dr. Brick was stung by some insect while bathing and the larva was 
extracted after about six weeks. It gave rise to excruciating pain at 
intervals, owing, as he inferred even before the determination of the 
cause, to ' something alive beneath the skin.' It was at first ' a con- 
siderable tumefaction over the tibia, which had the appearance of an 
ordinary boil (phlegmon) ; in the center there was a small black speck.' 

1 Ward, H. B., 1903. On the Development of Dermatobia hominis. Mark 
Anniversary Volume, Article XXV, pp. 483-512. (Includes a discussion of 
synonymy of species). 



MYIASIS 



259 



The tumor began to discharge at about four weeks, and was so serious 
that he was ' scarcely able to walk.' Scarifying the tumor yielded no 
results, and finally poulticing with cigar ashes and rum for five days 
resulted in the extraction of the larva dead. Dr. Brick records that ' it 
had traveled on the periosteum along the tibia for at least two inches.' 
While other authors hold very generally that the larva always inhabits 
a fixed spot in the subcutaneous tissues, I do not find that any one 
has referred to this record of migration made by a most competent 
observer." 

The following observation made by Miller (Journ. Amer. Med. Assoc, 
Vol. LV, pp. 1978-1979) throws more light on the matter of migration, 
although in this case the grub was Hypoderma lineata. "In December, 
1907, the boy noticed a small round lump just below the left knee ; this 
lump was slightly red and very tender, especially at night. About two 
days later the lump had disappeared from its original position and was 
found some three inches above the knee ; the following day it was still 
higher in the thigh, and during successive days it appeared at different 
points along a course up the abdomen, under the axilla, over the scapula, 
up the right side of the neck, irregularly about the scalp, finally passing 
back of the ear and to the submental region, which it reached about two 
months after its first appearance ; there it remained stationary. The 
extracted larva was identified by Doctor Stiles as Hypoderma lineata." 

Identification of Myiasis-producing Larvae. — The value of a simple 
method for the identification and classification of dipterous larva? 
involved in myiasis is no 
doubt evident to the student 
of this subject. Instances are 
few in which the larva? can be 
reared to the adult condition, 
when identification could of 
course be readily made. 
Authorities are now for the 
most part agreed that the 
posterior spiracles afford the 
most useful diagnostic char- 
acters, since these, while dif- 
fering consistently in position, 
form and structure for the 
genera and species, show little 
or no variation within the 
species except in a few species 
in the very early stage immediately after hatching. 

To prepare the specimen for study it is necessary to first remove by 
means of a sharp razor the extreme posterior end (usually the broader), 
— a very thin section is needed. This section is then boiled until quite 
clear in a 2 per cent solution of potassium hydroxide (KOH), or by 




Fig. 168. 



Posterior view (stigmai tieid) of the 
larva of Calliphora vomitoria, showing stigmai 
plates. (1) ring; (2) button; (3) slit-like 
spiracles. 



260 MEDICAL AND VETERINARY ENTOMOLOGY 

soaking in xylol for a few hours, after which it is prepared in the 
usual way for microscopic study. 

It will be seen (Fig. 168) that there are two stigmal plates more or 
less separated from each other, within which are situated the spiracles, 
one to three in number, either slit-like, sinuous or more or less circular. 
There may or may not be present a " button," i.e. a prominence located 
at the narrower segment of the ring or periphery of the stigmal plate ; 
the " button " may or may not be present in the species possessing 
slit-like spiracles. 

In using the posterior spiracles as diagnostic characters, the above 
conditions are considered, i.e. (1) diameter of the stigmal plate, the space 
occupied by one stigmal plate on a line drawn through the center of both ; 
(2) length, when slits are absent, the space occupied by a plate on a line 
drawn dorsoventrally through the center of the plate ; or, when slits 
are present, the space occupied by a plate along a line drawn from the 
lower edge of button (or space if button is absent) through the longest 
slit (middle slit) to the margin of the plate ; (3) width, along a line drawn 
at the middle of the plate at right angles to the length line ; (4) distance 
between the plates ; (5) general form of the plates ; (6) shape of spir- 
acles ; (7) presence or absence of button ; (8) general structure of plate. 

The following key, 1 while still somewhat unsatisfactory, serves to 
classify the principal families of Diptera which include genera and 
species relating to myiasis. In this key the entire larva is needed for 
identification. 

KEY TO THE IDENTIFICATION OF LARVAE OF THE DIPTE- 
ROUS FAMILIES AND CERTAIN SUBGROUPS WHICH IN- 
CLUDE GENERA AND SPECIES RELATING TO MYIASIS 

I. (a) Body cylindrical, tapering anteriorly II 

(b) Body robust, ovate, cylindrical, rounded 

at the ends, slightly depressed ........ (E strides 

e.g. Gastrophilus equi, (Estrus 
ovis, Hypoderma lineata 

(c) Body elliptical, much depressed dorso- 

ventrally ; segments provided 

with long spiny processes . . . . . . . . . Homalomyia 

(sub-group of Anthomyidse) 
e.g. Fannia (Homalomyia) 
canicularis, Fannia (Ho- 
malomyia) scalaris 

(d) Body with long tail-like process Eristalis 

e.g. Eristalis tenax 
II. (a) With one anterior hooklet ; stigmal field 
slightly depressed; area sur- 
rounding stigmal field usually de- 
void of tubercles, which if present 

1 The author is indebted to Mr. I. M. Isaacs for much careful and tedious 
work in the construction of the above key. 



MYIASIS 



261 



are small and insignificant; 
spinose areas only on ventral sur- 
faces of segments 

(6) With two anterior hooklets .... 
III. (a) Posterior spiracles with sinuous slits . . 



(b) Posterior spiracles with three short 
straight slits in each plate; few 
faint tubercles around stigmal 
field 



. . Ill 

• ' . IV 

Muscina 



Muscidce (except 

subgroup) 
e.g. Musca domestica, Sto- 

moxys calcitrans, Hcema- 

tobia serrata 



IV. (a) Spinose areas completely surrounding 
segment and occasionally supple- 
mentary pads on the lateral sur- 
faces 

Stigmal field depressed and sur- 
rounded by prominent tubercles ; 
posterior spiracles with three dis- 
tinct slits in each plate ; plates 
directed more or less toward each 
other 



. . . Muscina subgroup 
e.g. Muscina stabulans 



(1) 



(1) or (2) 



e.g 



(2) 



Very small (not over 4-5 mm.) ; an- 
terior spiracles with few, but com- 
paratively long lobes; posterior 
spiracles on end of two cylindrical 
processes extending posteriorly 
from the dorsal part of the tips of 
the body 



. . . . Sarcophagida? 
Calliphora vomitoria, 
Calliphora erythrocephala, 
Lucilia ccesar, Lucilia 
sericata, Chrysomyia 

macellaria, Auchmero- 
myia luteola 



(6) Spinose areas on ventral and lateral sur- 
faces; stigmal field slightty de- 
pressed and surrounded by short 
fleshy tubercles 



(c) Body segments with spinose areas only 
on ventral surfaces ; anterior spir- 
acles with a large number (20 ± ) 
of lobes ; slightly depressed or flat 
stigmal field ; no tubercles ; pos- 
terior spiracles with three short 
almost parallel slits, those of one 
plate pointing toward those of the 
other ; plates lacking brown chi- 
tinous borders; anal tubercles 
prominent, rounded and flattened , 



Drosophilidce 

e.g. Drosophila ampelophila 



Anthomyida (except Homalo- 

* myia subgroup) 
e . g . A n th omyia radicum, Phor- 
bia brassicce 



Trypetidce 

e.g. Ceratitis capitata, Dacus 
oleoe 



262 MEDICAL AND VETERINARY ENTOMOLOGY 

The following species may be more or less easily identified : 

Family Muscidce 

Musca domestica, Linn. Stigmal field usually slightly concave and the 
surrounding area devoid of distinct tubercles ; stigmal plates prominent, 
somewhat longer than wide, D-shaped, flat sides facing, about one third 
diameter apart ; spiracles apparently three in number and sinuous ; 
button absent in first stage on hatching ; button present thereafter, 
large and very dark, embedded near the center of the flattened side of 
stigmal plate ; ring heavy and dark. (Larva of house fly.) 

Stomoxys calcitrant, Linn. The stigmal field is slightly convex and 
is in the dorsal half of the posterior end. There are no tubercles out- 
lining the field. The species can easily be recognized not only by the size 
and shape of the spiracles but by the distance between the two plates, 
there being from two and a half to three diameters between them. The 
plates themselves are small, triangular in shape and black in color. In 
this species each of the slits is surrounded by light areas which appear in 
each corner of the triangular plates. (Larva of biting stable fly.) 

HcBmatobia serrata R. Desv. The stigmal field of H. serrata is 
neither depressed nor outlined by tubercles. In shape the stigmal 
plates are D-shaped, as are those of M . domestica, but are proportion- 
ately much narrower. They are very dark in appearance, due to the fact 
that the black chitinous edges are joined to the comparatively large 
black button, by three wide chitinous stripes. Portions of the sinuous 
slits may be seen in the small clear spaces left between the stripes. 
The three-part division of the surface is very similar to that found in 
the spiracles of Stomoxys calcitrans. The plates are about one fourth 
of their diameters apart and therefore close together compared to Musca 
domestica. In some cases there is a tendency toward a slightly triangular 
shape in the spiracles. (Larva of horn fly.) 

Muscina stabulans Fallen. The stigmal field is not depressed and 
faint tubercles may be seen dorsal to it. The spiracles are fairly promi- 
nent, almost round in «shape with the inner border slightly flattened, 
black, with three short slits in each plate pointing toward those of the 
opposite plate, and from one third to one half a diameter apart. (Larva 
of non-biting stable fly.) 

Family Sarcophagidw 

Calliphora erythrocephala Mg. The stigmal field is slightly de- 
pressed. The stigmal plates are small and about one diameter apart. 
The slits in each plate converge more than do those of the other species 
mentioned and point almost directly toward those of the opposite plate. 
In the first period the plates are about as long as they are wide, occasion- 
ally being slightly wider, there being no button. In the second period 



MYIASIS 263 

they are slightly longer than they are wide, there being a prominent, 
bullet-shaped button, and the ring is dark and very heavy. (Blue- 
bottle fly larva.) 

Lucilia ccesar Linn. The stigmal field is slightly depressed and is 
outlined by somewhat fleshy tubercles. The stigmal plates themselves 
are longer than they are wide and are considerably larger than are those 
of C. erythrocephala. A well-developed button is present. The ring 
is thin and delicate. The slits, although directed more or less toward 
those of the opposite plate, point more toward the ventral surface than 
do those of C. erythrocephala and do not converge as much. (Larva of 
the greenbottle fly.) 

Lucilia sericata Mg. The stigmal field is well depressed and is 
outlined by tubercles more or less conical but not very sharp. The stig- 
mal plates are comparatively large in both the first and second period. 

In the first period the plates are wider than they are long and are 
close together, being only about one eighth of a diameter apart. The 
slits are long and rather narrow, pointing ventrally, those of one plate 
being directed in some measure toward those of the opposite plate. 
There is no button. 

In the second period the plates are proportionately longer than in the 
first period and they are about one fourth of a diameter apart. The slits 
also are wider in proportion and although still directed ventrally they 
point slightly more toward those of the opposite plate. Care must be 
taken as to the exact meaning of length and width in this species. 
(Larva of sheep maggot fly.) 

Chrysomyia macellaria Fabr. The stigmal field is a very deep 
depression of the dorsal half of the posterior end. The depression is so 
deep that the lip-like edges of the last segment almost conceal the 
spiracles. Outlining the stigmal field are small but sharp tubercles. 
The stigmal plates are fairly large and are about as long as they are 
wide. There is no button. In the first period the plates are about 
one fourth of a diameter apart, while in the second period they are a 
little over one half of a diameter apart. The slits point ventrally, 
those of one plate being directed in some measure toward those of 
the onnnsite plate. (Larva of Texas screw worm fly. N 

Family Anthomyidw 

Fannia (Homalomyia) canicularis Linn. Each segment is provided 
with long, bristly, sharp, spiny processes. The posterior spiracles are 
situated on the anterior part of the last segment, they are raised, three- 
lobed processes. The lobes are distinct and can easily be seen. The 
larvae are about 8 mm. in length when fully grown. (Larva of the lesser 
house fly.) 

Fannia {Homalomyia) scalaris Fabr. The processes on each seg- 
ment are feathery rather than sharp or spiny and are not quite as long as 



264 MEDICAL AND VETERINARY ENTOMOLOGY 

the processes of F. canicularis. The posterior spiracles also differ in the 
two species, the lobes not being as well marked in F. scalaris. The 
larvse are from 7 to 8 mm. in length when fully grown. The feathery 
appearance of the processes on the segments as compared to the 
spiny condition in F. canicularis is, however, most useful in distinguish- 
ing the two species. (Larva of the latrine fly.) 

Family Trypetidce 

Ceratitis capitata Wied. The stigmal field as a whole is not de- 
pressed nor is it outlined by tubercles, but occasionally each stigmal 
plate appears to be situated in a slight depression of its own. The 
plates are fairly prominent and are about twice as wide as they are long. 
In accordance with the group character, there is no visible chitinous 
edging outlining the plates. The slits of each spiracle are almost parallel 
and point directly toward those of the opposite plate. The spiracles 
differ from those of D. ole& only in the distance separating the two 
plates, they being about one diameter apart. (Larva of Mediterranean 
fruit fly.) 

Dacus olece Meig. The appearance of the stigmal field and pos- 
terior spiracles of this species are very much like those of the previous 
species, except for the fact that the plates are from one and a half to two 
diameters apart. As in C. capitata there is no chitinous border out- 
lining the spiracles, which are about twice as long as they are wide. 
The short straight slits of one plate point almost directly toward those 
of the opposite plate. (Larva of olive fly.) 

Family (Estridw 

Gastrophilus equi Fabr. One of the smallest of the (Estridas. A 
full-sized larva is about 17 mm. in length and 8 mm. in width at its widest 
part. It is compressed, in some measure, dorsoventrally. It is wide 
and thick near the posterior end and tapers almost to a point anteriorly. 
The spines surrounding each segment are large and sharp. The two 
anterior hooks are prominent. 

The stigmal field of this species is drawn well into the anterior por- 
tion of the last segment and is completely covered and protected by a 
prolongation of the outer edges of this segment. 

On a hard, chitinous background are six long, large, bent slits, bilater- 
ally placed, three on either side of a small diamond-shaped hollow. 
(The larva of the horse botfly.) 

Hypoderma lineata De G. is a large and fleshy grub and when fully 
developed is about 25 mm. in length and 11 mm. in width at its widest 
part. It is considerably depressed dorsoventrally and the segments 
are spinose although the large separate spines found in Gastrophilus equi 
are not present. 



MYIASIS 265 

The stigmal field is depressed but is not covered by any prolongation 
of the edges of the last segment. The spiracles are large, close together 
and grossly granular in appearance, in some cases being more or less 
furrowed. A good-sized button is embedded near the inner border of 
each plate and in many cases a clear ungranulated stripe is found on the 
chitinous background between the button and the inner border. The 
plates usually appear to be dark brown with the button a little lighter in 
color. (The ox warble.) 

CEstrus ovis Linn., when fully developed, is about 28 mm. in length 
and 8-10 mm. in width. It is, therefore, longer and narrower than H. 
lineata, a condition which gives it a more rounded appearance. The 
dorso ventral compression, however, is noticeable. The segments are 
spinose. 

The stigmal field is depressed. The plates are roughly round, with 
the inner borders flattened. The plates are very dark, finely granular 
in appearance with a somewhat indistinct button in the center of each 
plate. (The sheep head maggot.) 



CHAPTER XVII 



FLEAS AND LOUSE FLIES 

A. Fleas 

Order Siphonaptera 

Structural Characteristics. — Fleas are laterally compressed, wing- 
less, highly chitinous, mostly leaping insects of small size, inhabiting by 
preference certain warm-blooded hosts and are blood-sucking in both 
sexes. In size the common fleas vary from 1.5 to 4 mm. in length, 
according to the species, though there is comparatively little variation 
within a given species. The males are as a rule somewhat, often con- 
siderably, smaller than the females. Nearly all fleas have the ability 
to leap, though the Chigoe fleas, especially the females, are more or less 
sessile. 

The posterior edges of the abdominal segments are provided with 
backward-extending spines, which hinder backward motion through the 

hair of the host. The piercing mouth 
parts (Figs. 169-170) of the adult fleas 
are flattened, blade-like structures con- 
sisting of a pair of triangular maxillae 
with jointed palpi between which are 
located the organs of the proboscis 
proper, i.e. an outer pair of structures 
comprising the labium which ensheaths 
loosely the inner, more slender stylets, 
— a pair of mandibles with . serrate 
edges, and a smooth labrum (hypo- 
pharynx?). On the small head are 
also located the sunken antennse with 
annulated knobs, and the inconspicuous 
simple eyes (absent in some species). 
In some species of fleas the head is 
provided with rows of spines (Fig. 171), 
the ctenidia, a valuable characteristic in classification; the ctenidia 
may be located just above the mouth parts and are then said to be 
oral, or may be situated back of the head and are then thoracic or 
pronotal (both sets may be present) . 

The legs consist of Rve joints ; viz. the coxa (the joint nearest the 

266 




Fig. 169. — Photomicrograph of the 
mouth parts of a flea, — front view. 
(For identification of parts see next 
figure.) 



FLEAS AND LOUSE FLIES 



267 



body), the trochanter, sl very small segment between the coxa and the 
femur, the tibia (strongly spined), and the five-jointed tarsus terminating 
in a pair of ungues or claws (Fig. 171). 

Life History. — The eggs of the flea (Fig. 172a) are large (.5 mm. 
long), glistening white, blunt at both ends. Comparatively few eggs 
are deposited, the observed range being from 3 to 18. Most species 






palpus 



me>x'itU 




maxilUru 
palp** J 







Fig. 170. — Showing mouth parts of a flea. A, front view; B, side view 



deposit dry eggs and hence they do not become attached to the hairs 
of the host even though oviposition has taken place there. There is 
every reason to believe that some species of fleas seldom or never de- 
posit their eggs among the hairs of the host, preferring the loose earth, 
excrement, dust, etc. Captured fleas will readily oviposit in glass vials 
or other receptacles. If deposited on a dog, for example, the dry eggs 
fall off readily when the animal stretches and shakes itself ; thus myriads 
of eggs may be found on the sleeping mat of a flea-infested animal. 

The length of time required for the egg stage depends largely if not 
wholly on temperature. High mean temperature from 35° C. to 37° C. 
inhibits development, which may account for the fact that the eggs do not 
hatch well on the host. At a temperature of from 17° C. to 23° C. Mitz- 
main 1 found that the egg stage lasted from seven to nine days ; at from 



1 Mitzmain, M. B., 1910. General observations on the bionomics of the 
rodent and human fleas. U. S. Public Health Service Bull. 38. 



268 MEDICAL AND VETERINARY ENTOMOLOGY 




FLEAS AND LOUSE FLIES 269 

11° C. to 15° C. it lasted about fourteen days. Atlantic Coast observers 
have found that this stage may be passed in from two to four days. 

The embryo is provided with a sharp spine on the head by means of 
which the egg shell is cut into shreds by a tumbling motion of its inhab- 
itant, which is thus liberated. The larvae (Fig. 1726) are very active, 
slender, 13 segmented, yellowish white maggots, with segmentally ar- 
ranged bristles. The mouth parts are of the biting type and the larvae 
subsist on organic matter. Very little food seems to be necessary for 
their development, though excrementous matter, e.g. feces from rabbits, 
rats, squirrels, and other rodents, also dry blood, sprouting grain, etc., 
favor growth. Excessive moisture is certainly detrimental to the life 




Fig. 172. — Showing life history of a rodent flea, a, eggs; b, larva; c, pupa in cocoon; 
d, pupa removed from cocoon; e, fleas, — male (lower), female (upper). X 12. 

of the larvae, although fewer fleas emerge from the cocoon during periods 
of hot dry weather. The larvae are usually found in the crevices of the 
floor under the carpet or matting, in dusty stables, coops, kennels, nests 
of rodents, etc. 

The length of the larval stage, during which there are two molts, 
is also influenced by temperature, and moisture in addition. Under 
laboratory conditions with room temperature this stage requires from 
twenty-eight to thirty days and over, though here again other workers 
report from seven to ten days. At the end of the larval period, the 
insect spins a silken, whitish cocoon (Fig. 172c) in which transforma- 
tion takes place. The pupa (Fig. 17 2d) lies within this cocoon. 

Warm, moist weather favors the metamorphosis of the pupa, from 
which the fully developed imago emerges in from ten to fourteen 
days. 

Mitzmain (loc. tit.) observed one individual of the squirrel flea 
(Ceratophyllus acutus Bak.) from egg to imago with the following results : 
egg stage, eight days ; first larval stage, six days ; second larval stage, ten 
days ; third larval stage, twelve days ; cocoon (pupal stage) , twenty-one 
days; total, sixty-seven days. 

The following table (Table XIII), after the same author, indicates 



270 MEDICAL AND VETERINARY ENTOMOLOGY 

the wide variation in length of life history as reported by various 
authorities. 

TABLE XIII 

Time Required for the Life Cycle of Fleas in Different Countries 
Compiled from Accounts of Various Authors (Mitzmain) 



Country and Species 
of Flea 


Egg 


Larva 


Pupa 


Complete 
Generation 


India : 

L. cheopis 

Australia : 

P. irritans 

Europe : 

P. irritans 

Ct. canis 

United States : 

Atlantic Coast : 


2 days 
6 days 


1 week 
12 days 


7 to 14 days 
14 days 


21 to 22 days 
4 to 6 weeks 


4 to 6 days 
2 weeks 


11 days 

12 days 


12 days 

10 to 16 days 


4 to 6 weeks 

5 to 6 weeks 


P. irritans ) 
Ct. canis j 


2 to 4 days 


8 to 24 days 


5 to 7 days 


2 to 4 weeks 


Pacific Coast : 

P. irritans .... 
L. cheopis .... 
C. acutus .... 
C. fasciatus . . . 


7 to 9 days 
9 to 13 days 
7 to 8 days 
5 to 6 days 


28 to 32 days 
32 to 34 days 
26 to 28 days 
24 to 27 days 


30 to 34 days 
25 to 30 days 
24 to 27 days 
24 to 26 days 


9 to 10 weeks 
9 to 11 weeks 
8 to 9 weeks 
7 to 8 weeks 



Longevity of Fleas. — It is of great importance to know how long a 
flea will live with and without food under various conditions. If not 
provided with a moist medium in which to live and at the same time de- 
prived of the opportunity of feeding on a warm-blooded animal the 
majority of fleas die in about six days or less. In a moist medium such 
as wheat grains and sawdust (moistened), Mitzmain has kept squirrel 
fleas alive from thirty-eight days in one case to sixty-five days in 
another, the former a male, the latter a female. Rat fleas on human 
blood alone averaged eight and one half days (maximum seventeen) for 
the males, and thirty-two and four fifths days (maximum one hundred 
and sixty) for the females. 

Hosts and Occurrence of Species. — As will be seen later in this 
chapter, the rodent fleas are most important from the public health stand- 
point, and transference from host to host of different species is a well- 
known habit, adding much to the danger of disease transmission. 

It is true that ordinarily a certain species of flea is found to predomi- 
nate on a given species of host, for example Ctenocephalus canis Curt, 
on the dog, Ceratophyllus fasciatus Bosc. on the rat in the United States, 
Xenopsylla cheopis Roth, on the rat in India, Ctenopsylla musculi Duges 
on the mouse, Pulex irritans Linn, on the human, etc. 

For example, in an unpublished report to the writer on the species of 
fleas found on rats in San Francisco, Rucker states that a great prepon- 
derance of the rat fleas recovered in San Francisco are Ceratophyllus 
fasciatus as based on 10,972 specimens as follows : 



FLEAS AND LOUSE FLIES 



271 



Ceratophyllus fasciatus 68.07 % 

Xenopsylla (Lcemopsylla) cheopis .21.36% 

Pulex irritans 5.57 % 

Ctenopsylla musculi 4.48 % 

Ctenocephalus canis 52 % 

The following tables (Tables XIV-XX) adapted after McCoy 1 
throw much light on the interchange of hosts and predominance of 
species : 

TABLE XIV 
From Brown Rats (Mus norvegicus) 



No. of Rats 


C. FASCIATUS 


L. CHEOPIS 


P. IRRITANS 


Ct. MUSCULI 


Ct. canis 


Combed 


Male 


Female 


Male 


Female 


" Male 


Female 


Male 


Female 


Male 


Female 


606 


570 


1252 


790 


1146 


225 


425 


44 


137 


13 


15 



TABLE XV 
From Black Rats {Mus rattus) 



No. of Rats 


C. FASCIATUS 


L. CHEOPIS 


P. IRRITANS 


Ct. musculi 


Ct. 


3ANIS 


Combed 


Male 


Female. 


Male 


Female 


Male 


Female 


Male 


Female 


Male 


Female 


11 


7 


32 


6 


5 








4 


17 





2 



TABLE XVI 

From Mice (Mus musculus) 
From an unknown number of Mus musculus 





C. FASCIATUS 


L. CHEOPIS 


P. IRRITANS 


Ct. musculi 


Ct. canis 




Male 


Female 


Male 


Female 


Male 


Female 


Male 


Female 


Male 


Female 




1 


5 


2 











3 


10 






1 McCoy, George W., 1909. Siphonaptera observed in the Plague Cam- 
paign in California, etc. U. S. Public Health Reports, Vol. 24, No. 29. 



272 MEDICAL AND VETERINARY ENTOMOLOGY 

TABLE XVII 
From California Ground Squirrels (Citellus beecheyi) 



No. of Squirrels 


C. ACUTUS 


Hop. anomalus 


Combed 


Male 


Female 


Male 


Female 


132 


2065 


2306 


86 


140 



TABLE XVIII 

From the Dog (Canis familiar is) 



No. 


Ct. 


CANIS 


P. IRRITANS 


Ct. felis 


C. ACUTUS 


Combed 


Male 


Female 


Male 


Female 


Male 


Female 


Male 


Female 


4 


10 


44 


8 


17 





1 


1 






TABLE XIX 
From the Cat (Felis domestica) 



No. Combed 


Ctenocephalus felis 


Male 


Female 


2 


5 


15 



TABLE XX 
From Man (Homo sapiens) 



No. OF 
Individ- 
uals 


P. IRRITANS 


Ct. felis 


Ct. canis 


C. ACUTUS 


Male 


Female 


Male 


Female 


Male 


Female 


Male 


Female 


29 


117 


220 


1 





1 





1 


2 



FLEAS AND LOUSE FLIES 273 

Light Reactions. — In a series of light reaction experiments by the 
writer on two species of fleas, Pulex irritant and Ceratophyllus acutus, it 
was found that the former reacts positively and directly to light (incan- 
descent) at 10 CM., 83+ CM. and 100 CM., and is indifferent to 7- 
C.M., while the latter species reacts negatively to higher intensities, 
such as 46+ CM. and 83+ CM., and is indifferent to lower intensities 
such as 9+ CM. and 7— CM. 

The larvae of C. acutus react in the main positively to light in their 
early stages, becoming more and more negative as they grow older. 
An intensity of 8.38 CM. was used at intervals of three and five days. 

Chemical Experiments. — To determine the lethal property of va- 
rious chemicals, a series of experiment vials were made after the fashion 
of cyanide bottles for killing insects, i.e. a chamber was prepared into 
which cotton was placed soaked in the material to be tested and covered 
with dry blotting paper, the fleas thus did not come in direct contact with 
the chemical. 

It was found that certain essential oils, such as lavender, citronella, 
mirbane, caraway, peppermint, eucalyptus and pennyroyal have a 
stupefying effect on fleas when used in strong concentrations, 50 per cent 
and over. It is quite probable that rubbing the body, particularly with 
oil of citronella, would act as a fairly good repellent. 

Systematic. — Over 300 species of fleas have been described, of which 
number only a few need to be considered here, particularly those affecting 
rodents and man. The Siphonaptera (also referred to as Aphaniptera) 
are commonly divided into three families, viz., Sarcopsyllidse, Pulicida? 
and Ctenopsyllidse. The following keys for the classification of fleas 
together with descriptions are adapted mainly after Banks. 1 

1. Thoracic segments much shortened and constricted : labial palpi apparently 

not jointed; third joint of antenna? without subjoints; no ctenidia; 
abdomen of female becomes more or less swollen . . Sarcopsyllidce 
Thoracic segments not shortened nor constricted ; labial palpi with joints ; 
third joint of antennae with several more or less distinct subjoints ; ctenidia 
often present ; abdomen of female never distinctly swollen .... 2 

2. Posterior tibial spines in pairs Pulicidce 

Posterior tibial spines mostly single and more numerous . Ctenopsyllidce 

Family Pulicidce 

1. Head without ctenidia; eyes distinct 2 

Head and pronotum with ctenidia ; last tarsal joint with four pairs of lateral 

spines 5 

2. Pronotum without ctenidia 4 

Pronotum with ctenidia 3 

3. Female with one antepygidial bristle on each side . . . Hoplopsyllus 
Last tarsal joint with five pairs of lateral spines; female with two to five 

antepygidial bristles each side Ceratophyllus 

1 Banks, Nathan, 1910. The ectoparasites of the rat. A symposium on 
"The Rat and its Relation to the Public Health." U. S. Pub. Health Service 
Bull., Washington, D.C. 



274 MEDICAL AND VETERINARY ENTOMOLOGY 

4. Mesosternite very narrow, without internal rod-like incrassation from the 

insection of coxa upward Pulex 

Mesosternite with a rod-like internal incrassation from insection of coxa 
upward Xenopsylla 

5. Eyes rudimentary; female with two to five antepygidial bristles each 

side Neopsylla 

Eyes distinct ; female with one antepygidial bristle each side Ctenocephalus 

Family Sarcopsyllidce 

" The fleas of this family are commonly called ' chigoes/ ' jiggers ■ 
or sand fleas. The head is usually larger proportionately than in other 
fleas ; there are no ctenidia on head or pronotum ; the thoracic segments 
are extremely short, and in the female the abdomen enlarges with the 
development of the eggs. They do not hop about as other fleas, but re- 
main on the spot to which they have attached themselves, until they 
die. Frequently the adjacent skin grows over them, forming a swelling 
of considerable size." 

1. Angle of head acutely produced ; fifth tarsal joint of hind legs without heavy 

spines ; few spines on the legs Sarcopsylla 

Angle of head not produced, obtuse; fifth tarsal joint with heavy lateral 
spines and other spines on other parts of the legs . . Echidnophaga 

Family Ctenopsyllida? 

" To this family belongs the Ctenopsylla musculi Duges (Fig. 173). 

" This was formerly placed in the genus Typhlopsylla. The head is 
rather acute in front and has four ctenidia each side ; the eyes are very 
small ; the pronotal comb has 22 spines ; each dorsal segment of the 




Fig. 173. — Ctenopsylla musculi, a mouse flea ; male, right ; female, left. X 17. 

body has two rows of hairs ; the basal row of smaller hairs. The pro- 
portions of joints in the hind tarsus are: 45-25-17-8-14. Length 1.8 
to 2.5 mm. This species is abundant on rats and mice in Europe and 
other countries ; recently it has been taken in California and Florida 
on rats and mice." 



FLEAS AND LOUSE FLIES 

The Commoner Species 



275 



Pulex irritans Linn. (Fig. 174). "The mandibles reach about half- 
way down on the anterior coxae ; the head is regularly rounded in 
front ; two bristles on the gena, one placed low down just above the 
maxilla, the other below the eye ; there are no transverse rows of bristles 




Fig. 174. — Pulex irritans, the human flea ; male, right ; female, left. X 17. 

on the vertex, and but one row of bristles on each abdominal tergite. 
The proportions of the joints of the hind tarsus are : 5-30-18-12-32. 
Color, usually yellow-brown. Male, 1.6 to 2 mm.; female, 2 to 3.5 
mm. 

" This, the human flea, is quite cosmopolitan, but more abundant in 
warm countries than elsewhere. It occurs on many domestic animals 
and has frequently been taken from rats in California and elsewhere ; 
it also occurs on skunks." 

Ctenocephalus cards and felis (Fig. 175). "The common fleas on 
cats and dogs, as well as on man, belong to two species long kept under 





Fig. 175. — Ctenecephalus canis, the cat and dog flea; male, left; female, right. X 17- 

one name (C. canis or C. serraticeps) , but lately shown by Rothschild 
to be distinct. Both have a comb of eight spines on the head and sixteen 



276 MEDICAL AND VETERINARY ENTOMOLOGY 

spines in pronotal comb ; the proportions of joints in the hind tarsus are : 
40-24-15-10-24. They may be separated as follows : 

1. In the female the head is fully twice as long as high (seen from side) ; the 
first spine of genal comb is two thirds the length of the second ; in male 
the manubrium of claspers is barely enlarged at tip ; and with two rows 

of hairs on disk of movable finger C. felis Bouche 

In the female the head is less than twice as long as high (seen from side) ; 
the first genal spine in the head comb is only about one half the length 
of the second; in the male the manubrium of clasper is very distinctly 
enlarged at tip; but one row of hairs on the disk of the movable 
finger C. canis Curtis 

Ceratophyllus fasciatus Bosc. (Fig. 176). "There are eighteen or 
twenty spines in the pronotal comb; there are three bristles in front 
of eye and in female two, and in male four in front of these ; there are 




Fig. 176. — Ceratophyllus fasciatus, the rat flea ; male, left ; female, right. X 17. 



three or four hairs on the inner surface of the hind femur ; the propor- 
tions of joints in the hind tarsus are : 50-33-20-1 1-21 . The manubrium 
of the male claspers is very long and slender, and some of the bristles 
on the movable finger are as long as the joint. Length, male, 1.8 mm. ; 
female, 2.5 mm.- 

" It has been recorded in California in rats, mice, skunks and man. 
It is also common in Europe and elsewhere on rats, mice and other 
small animals." 

Ceratophyllus acutus Baker (the squirrel flea) (Fig. 177). "This 
species is readily known by having a spine at tip of the second joint 
of hind tarsus longer than the third joint and reaching over on to the 
fourth joint; the abdominal tergites have each two rows of bristles; 
the male claspers are very large and long, sickle shaped. Color, pale 
brown. Length, 3 to 3.5 mm." 

Ceratophyllus niger Fox. "This species has the pronotal ctenidia 
of about 26 spines ; there are a few hairs on the inner surface of hind 
femur; apical spines of second joint of hind tarsus not longer than 
third joint ; three hairs in front of the eye and three in front of these ; 



FLEAS AND LOUSE FLIES 



277 



movable finger of claspers with five slender bristles on the outer edge. 

Color, very dark brown. Length, 3.5 mm. 

"Taken in California from Mus decumanus and from man." 
Ceratophyllus londinensis, Rothsc. " This species is closely allied 

to C. fasciatus, and best separated from it by the shape and armature 

of the genital parts; the manubrium is not as long as in that species, 




Fig. 177. — Ceratophyllus acutus, the squirrel flea ; male, right ; female, left. X 17. 

and the bristles on the movable finger are shorter ; the third joint of 
the maxillary palpi is proportionately longer than in C. fasciatus. There 
are three bristles in front of the eyes and four or five in front of these ; 
there are a few hairs on the inner surface of the hind femur ; the propor- 
tions of the joints in the hind tarsus are : 46-30-18-11-18. 

" It has been recorded by Dr. Fox from M us rattus in California, 
and is known from rats and mice from several parts of Europe." 

Xenopsylla cheopis Rothsc. (Fig. 178). "The mandibles reach 
nearly to the end of the anterior coxae ; there are no ctenidia on the 





Fig. 178. — Xenopsylla cheopis, the oriental rat flea; male, left; female, right. X 17. 

head or pronotum ; two bristles on gena ; oral bristles placed low down 
just above the base of the maxilla ; ocular bristle in front and just above 



278 MEDICAL AND VETERINARY ENTOMOLOGY 

the middle of the eye ; the eyes are distinct ; each abdominal tergite 
has but one row of bristles ; the hind femur has a row of about eight 
bristles ; the proportions of the joints in the hind tarsus are as follows : 
40-30-16-10-20. Color, light brown. Male, 1.5 to 2.0 mm.; female, 
2 to 3.0 mm. 

' ' This is a true rat flea, but will readily bite man, and is the species 
chiefly concerned in transmitting the bubonic plague. It is widely 
distributed, especially in seaport towns." 

Hoplopsyllus anomalus Baker. " The mandibles scarcely reach 
halfway down on the anterior coxa? ; upon each are two large spines ; 
the pronotal comb has about nine spines each side ; and each abdominal 
segment has but a single row of bristles. The hind femora have six to 
eight bristles on the side; the proportions of the joints in the hind 
tarsus are : 26-16-8-5-13. Color, dark reddish brown. Female, 2.5 
mm.; male, 1.5 mm. 

" Described from a spermopile from Colorado and recorded by Dr. 
Fox and Professor Doane from Mus norvegicus from California." 

EchidnopJiaga gallinacea Westw. " This species has the body almost 
as broad as long, and of a red-brown color ; one bristle in front of eye 
and six on each metathoracic pleuron; each abdominal tergite has 
on each side near the median line a single hair; the spiracles are 
situated well down on the sides. Length: male, 0.8 to 1.2 mm; 
female, 1 to 1.8 mm. 

" This species is a fairly common pest of poultry and dogs in warm 
countries, and is called the ' chicken flea,' or ' stick tight/ ' 

Sarcopsylla penetrans Linn. This species differs from the above 
in that the eyes and antenna? are situated in the anterior half of the 
head, and the metathoracic scales are rounded. 

Plague. — Plague is a bacterial disease traceable to Bacillus pedis, 
runs a rapid course, presents a high mortality, 20 per cent to 95 per 
per cent, depending upon hygienic and social conditions, and while it has 
appeared in devastating epidemics in temperate climates, it is endemic 
in certain warmer countries, particularly southern India and China. 

Three forms of the disease may be considered; namely, bubonic, 
septicemic and pneumonic. The incubation period varies from two 
to eight days ordinarily, according to Manson, though longer and 
shorter periods have been observed. In the bubonic plague, which 
constitutes by far the greater percentage of the cases, there appear 
characteristic swellings (buboes) in the groin (femoral glands), axilla 
(axillary glands) or other parts. These buboes vary from 2 cm. to 
10 cm. in diameter; these appear within a day or two. In septicemic 
plague the bacilli appear in the blood in large numbers, there is a com- 
parative absence of swellings, the disease is very virulent and runs a 
very rapid course, terminating in death in from one to three days. 

In pneumonic plague the seat of the disease is the lungs. This form 
is considered most fatal and most infectious. 



FLEAS AND LOUSE FLIES 279 

The plague bacillus was discovered concomitantly and independently 
by Kitasato and Yersin in 1894, when it became established that rat 
plague and human plague are identical. Epidemics of plague in humans 
have evidently always been announced by fatal epizootics among rats. 

Plague Transmission. — Many theories have been advanced to ac- 
count for the transmission of plague, notably soil and climatic conditions, 
but apparently insects were not suspected until the latter part of the 
last century. Xuttall 1 in 1897 demonstrated the presence of B. pestis 
in the bodies of bedbugs (Cimex lechdarius) which had fed on the bodies 
of rats sick of plague. Simond 2 in 1898 first succeeded in transmitting 
plague from a sick rat to a healthy rat through the agency of infected 
fleas. Simond's work was discredited for a number of years, but was 
successfully repeated by Yerjbitski 3 in 1903. 

Liston 4 in 1904, working in Bombay, came to the following con- 
clusions : (1) There was one flea infecting rats in India far more commonly 
than did any other, viz., Xenopsylla (Pulex) cheopis Rothsc. ; (2) that 
these fleas when feeding on a plague rat harbored the plague bacillus 
in their bodies and that it multiplied therein; (3) that where fatal 
plague occurred many of these infected fleas were at large, and (4) that 
after a local epizootic of rat plague, man was also found to harbor these 
rat fleas and might become infected as had the guinea pigs used in the 
experiment. 

The following is a summary of experiments conducted by the Indian 
Plague Commission before and after its organization in 1905. 

In the first instance healthy rats were confined in close proximity 
to rats which, inoculated with plague, had succumbed to that disease, 
and that previous to this had been artificially infected with rat fleas 
(X. cheopis). The separate confinement of the rats in each case was 
so arranged that both contact with and access to all excreta were ex- 
cluded, although it was provided that the fleas could pass from the 
inoculated to the healthy rats ; this transfer actually did take place 
and in many cases these fleas contained virulent plague bacilli ; and 
when healthy non-immune rats were thus infected they died of plague 
to the extent of 79 per cent ; this extent of infection fell to 38 per cent, 
when partly immune rats of local origin were employed. 

That the plague had originated in the healthy rats through the 
intermediary of the rat fleas was further demonstrated by the fact that 
when they were actually transferred from artificially plague-infected to 
healthy English rats, the disease resulted to the extent of 61 per cent. 

Further, on constructing a series of miniature houses (godowns) so 

iNuttall, G. H. F., 1897 (loc. cit.). 

2 Simond, P. — L. S., 1898. La propagation de la peste. Ann. de lTnst. 
Pasteur, Vol. XII, p. 625. 

3 Verjbitski, D. T., 1908. The part played by insects in the epidemiology 
of plague. Journ. of Hyg., Vol. VIII, p. 162. 

4 Liston, W. G., 1905. Plague rats and fleas. Journ. Bombay Nat. 
Hist. Soc, Vol. XVI, pp. 253-273. 



280 MEDICAL AND VETERINARY ENTOMOLOGY 

as to reproduce the conditions pertaining to ordinary domiciles, it was 
found that whenever these were so constructed as to admit rats to 
their roofs, but not to their interiors, guinea pigs confined therein be- 
came successively infested by rat fleas and infected by plague, but that 
in those houses to which rats could not gain access plague was originated 
in guinea pigs living therein, either by transferring rat fleas to them, 
derived from plague-infected guinea pigs, or on accidental admission of 
rat fleas from other sources. Also, that when so confined, guinea pigs 
had, under these conditions, died of plague; healthy flea-free guinea 
pigs, subsequently introduced, became plague smitten, and that the 
contagion remained in the place in proportion as the test animals were 
accessible to, and were found to be infested with, fleas. In other words, 
that " if the fleas be present, the rate of progress being in direct propor- 
tion to the number of fleas present." Further, that when in one of 
the houses, to the interior of whose roof fleas could not gain access, 
healthy guinea pigs were confined, guinea pigs became flea infested and 
infected when running on the ground, to a less extent when the cage 
was placed two inches therefrom, and not at all when it was suspended 
two feet above it. The fact that infection took place where rats were 
located two inches above the ground indicates that contact with infected 
soil is not necessary for plague to originate, and that " an epizootic of 
plague might start without direct contact of healthy with infected 
animals." 

To demonstrate that this communication of plague from guinea 
pig to guinea pig was through the intermediary of fleas, rat fleas were 
taken from a morbid guinea pig and allowed to feed through muslin on 
healthy animals. The positive outcome of this experiment proved the 
above statement. 

The state of affairs that existed in actual domiciles in which plague 
occurred or had existed was next inquired into, advantage being taken 
of the fact that plague-susceptible guinea pigs would serve as hosts for, 
and for the collection of, fleas. 

Guinea pigs free from fleas were introduced into rooms in which 
persons had died of plague, or from which plague-infested rats had been 
taken. They were allowed to be at large in these rooms for periods of 
from eighteen to twenty-four hours. These guinea pigs not only col- 
lected the fleas on their bodies, most of which were rat fleas, but 29 
, per cent of them contracted plague and died of plague within a few 
days after being restored to ordinary confinement. As before, many 
of the fleas which they yielded harbored plague bacilli in their stomachs, 
and were capable of infecting additional animals. 

Further, after first washing the floors and walls of the rooms with 
an acid solution of perchloride of mercury, and so adequately disinfecting 
them for plague, but not for fleas, and then introducing guinea pigs, 
these latter became plague-infected if rat fleas were present. 

That the infection was actually due to fleas was also shown by the 



FLEAS AND LOUSE FLIES 281 

positive results from fleas collected from rats occurring in plague- 
infected houses and transferring them to healthy rats or guinea pigs in 
the laboratory. These in due course became infected and died of plague. 

Similarly fleas taken from the clean guinea pigs allowed to run in 
plague-infected houses, and transferred to fresh animals, communicated 
plague to them in eight out of forty experiments. 

In the next place, plague-free white rats, guinea pigs and monkeys 
were placed in enclosures, which precluded contact as well as soil in- 
fection, in plague-infested rooms, pairs of one animal or another being 
used in each of the forty-two experiments of this class conducted, one 
individual being confined to a flea-proof receptacle and the other to an 
adjacent one accessible to these insects (one animal being thus a control). 
In the latter case plague resulted in four instances, or 10 per cent gave 
positive results. 

As a variation of the same experiments, the enclosures for individual 
animals, whilst protected from soil or contact infection, were surrounded, 
as a screen to fleas, by 2| inches of " tanglefoot " or were unprovided 
with this protection, the " tanglefoot " being replaced by sand. 
(Twenty-nine experiments were conducted.) In the latter case the 
animal became infested with fleas, one having as many as twenty; 
seven became fatally infected with plague. In the former individual 
fleas were only found on three of the rats and no animals became plague- 
infected. 

Examining the fleas entrapped, 247 in number, it was found that 
147 were human fleas, 84 were rat fleas, and 16 cat fleas. Moreover, 
a large proportion of each kind was examined. Xo plague bacilli were 
found in the cat fleas, 1 only in 85 of the human fleas was infected, and 
no less than 23 out of 77 of the rat fleas harbored plague organisms. 

It was also shown that, when rats in the course of an epizootic died 
of plague, the pathological features manifested in their bodies corre- 
sponded to those exhibited by artificially rat-flea-infected animals, and 
hence it was inferred that in nature and under experimental conditions 
the animals had alike succumbed to a single agency. This ^identity 
especially related to the site in which buboes arose, that in both instances, 
where the place of inoculation could be observed was similar. 

Further Observations. — A study of mortality statistics shows that 
the greater percentage of plague occurs in the autumn, — September 
and October. This seasonal occurrence is undoubtedly due to climatic 
conditions, moisture and cold as affecting the life history and habitat 
of the rat and of the flea. Blue l reports a number of observations 
made in San Francisco indicating modes of infection; thus two small 
boys found the body of a dead rat in an unused cellar; the rat was 
buried with unusual funeral honors and in forty-eight hours both were 

1 Blue, Surgeon Rupert, 1910. Rodents in relation to the transmission of 
plague. U. S. Pub. Health Bulletin. The rat and its relation to the public 
health. 



282 MEDICAL AND VETERINARY ENTOMOLOGY 



taken ill with bubonic plague. Again, a laborer picked up a dead rat 
with the naked hand and threw it into the bay. He was taken ill with 
plague three days later. The case of a physician's family is also cited 
in which foul odors pervaded their second story flat over a grocery store. 
On removing the wainscoting around the plumbing to ascertain the 
cause of the odor, two rat cadavers were found in the hollow wall. In 
two or three days thereafter the two members of the family who used 
the room sickened, one dying on the fifth day of cervical bubonic plague. 
Blue believes that the removal of the wainscoting set free infected rat 
fleas. 

A most illuminating case is reported in the U. S. Public Health Re- 
ports (Nov. 7, 1913, p. 2356), viz. a fatal case of plague occurred in 
Manila (P. I.) in the person of an American, editor of the Manila Daily 
Bulletin. A plague rat had been found on September 6 in the block 
adjacent to the one in which the newspaper offices were located. The 
editor was admitted to the hospital September 19 and died at the Plague 
Hospital three days later. A mummified rat was found in the desk of 
the late editor, together with live fleas, Xenopsylla cheopis. Both the 
fleas and rat revealed bipolar staining organisms and inoculations into 
healthy laboratory rats produced typical cases of plague terminating 
fatally. 

The facts that the mummified rat must have been dead at least two 
weeks and that the live fleas contained plague bacilli causes the com- 
ment to be made that "these facts 
furnish strong proof that plague 
might be introduced into a country 
without either the importation of 
human or rat cases of plague and 
that fleas might be alone con- 
cerned." 

How the Flea Receives and 
Transmits Plague. — It was found 
by the Indian Plague Commission 
according to Fox (he. cit), that the 
average capacity of a flea's stomach 
(Xenopsylla cheopis) .was .5 cubic 
millimeter and that it might re- 
ceive as many as 5000 germs while 
imbibing blood from a plague rat. 
They further found that the bacillus 
would multiply in the stomach of a 
flea (Fig. 179) and that the per- 
centage of fleas with bacilli in the stomach varied with the season of 
the year. In the epidemic season the percentage was greatest for the 
first four days, and on one occasion the stomach was found filled with 
Bacillus pestis on the twentieth day. In the non-epidemic season no 




Fig. 179. — Showing Bacillus pestis from 
the intestine of a rat flea, Ceratophyllus 
fasciatus, taken from a plague rat. (Photo- 
graph by Mitzmain. Greatly enlarged.) 



FLEAS AND LOUSE FLIES 283 

plague bacilli were found in the stomach after the seventh day. They 
also found that in the epidemic season fleas might remain infective up 
to fifteen days, while in the non-epidemic season but seven days, and 
in the latter case the percentage of infection in animals was much less 
than in the epidemic season. They showed that while one flea was 
occasionally able to carry the infection this was not usual. It was found 
that both males and females were capable of transmitting the disease. As 
to the manner of dissemination the Commission found bacilli only in the 
stomach and rectum and never in the salivary glands nor body cavity 
and but rarely in the esophagus, and then only when the flea was 
killed immediately after feeding. As far as the writer knows the plague 
bacilli have not been demonstrated on mandibles, i.e. in a purely soiled 
condition, hence this fact and the absence of the bacilli from the salivary 
glands seems to preclude the possibility of direct inoculation by the 
bite, although it seems quite probable that plague bacilli might also be 
regurgitated, particularly when the flea's stomach is overfull and thus 
be injected at the time of biting. Very recently Bacot and Martin 1 
have come to the conclusion that plague can be transmitted during the 
act of biting when a temporary blocking or obstruction of the proventric- 
ulus takes place causing bacillus-laden blood to be forced back or re- 
gurgitated into the wound, thus producing infection. 

It will be observed that when a flea bites it commonly ejects feces 
and partially digested blood in the vicinity of the bite. It has been 
shown that an emulsion of plague flea feces placed upon the wound 
produced by the bite induces the disease in the animal, provided this 
is done within twenty-four hours after the insect has bitten, after which 
time the wound has probably healed sufficiently to exclude the organ- 
isms. The actual inoculation is, therefore, evidently an accidental 
process, i. e. the plague bacilli discharged per anum are rubbed into the 
bite of the flea either by the insect as it moves about or by the person in 
the act of scratching, — many persons very commonly scratch a flea bite 
until it bleeds. This method, together with that advanced by Bacot and 
Martin, probably explains the flea's role in the dissemination of plague. 

Squirrels and Plague. — Plague has been found in a number of 
species of rodents other than rats, notably ground squirrels (Citellus 
beecheyi) (Fig. 180). In California the disease was demonstrated in 
ground squirrels under natural conditions in 1908 according to McCoy. 2 
According to this author at the time of his writing (1910) about a dozen 
persons had contracted the disease under circumstances that pointed 
conclusively to squirrels as the cause. The two species of fleas com- 
monly infesting the ground squirrel in California are Ceratophyllus 
acutus Baker and Hoplopsyllas anomalus Baker of which the former 

1 Bacot, A. W., and Martin, C. J., 1914. Observations on the mechanism 
of the transmission of plague bv fleas. Journ. of Hygiene. Plague Supple- 
ment III, Jan. 14, 1914, pp. 423-439. 

2 McCoy, George W., 1910. Bubonic plague in ground squirrels. N. Y. 
Med. Journ., Oct. 1, 1910 ; see also U. S. Public Health Bulletin, No. 43. 



284 MEDICAL AND VETERINARY ENTOMOLOGY 



is far more numerous. McCoy proved the first-named species a carrier 
as follows. He inoculated a ground squirrel subcutaneously with a 
broth culture of B. pestis derived from a human case of plague. This 
squirrel died on the fifth day, but three days before its death, 100 fleas, 
C. acutus, were put in the cage with it. The dead animal was removed 

from the cage while warm, and 27 live 
fleas taken from its body. Smears 
made of the crushed bodies of two of 
these fleas showed an abundance of 
pest-like bacilli in each. The remain- 
ing 25 fleas were put in a clean cage 
with a healthy squirrel. This animal 
died of subacute plague 10 days later, 
the buboes being in the region of the 
median, posterior inguinal and pelvic 
glands. A pure culture of B. pestis 
was obtained from the liver. McCoy 
rightfully concludes that the experi- 
ment is conclusive in showing that 
C. acutus may convey plague from a 
sick to a healthy squirrel. The 
squirrels used in the experiment were 
kept in quarantine for at least a 
month prior to their being used, which 
was necessary to exclude any naturally 
infected ones. McCoy found the 
bacilli in squirrel flea feces four days 
after removal of the fleas from the host. 
Flea Control. (A) Fleas in the 
House. — The commonest household 
flea in Europe is Pulex irritans, the 
human flea, also predominating in 
California, while Ctenocephalus canis, 
the cat and dog flea, is commonest in 
the eastern portion of the United 
States. Both species are very often 
present at the same time, and both species infest cats and dogs; as a 
matter of fact they have a wide range of host animals. Unless house 
dogs and cats are very carefully groomed and repeatedly washed with 
efficient insecticides the presence of these animals will always be a source 
of many fleas. 

In treating a house for fleas it must be borne in mind that the larvae 
develop primarily in the crevices of the floors, under carpets and mat- 
tings. The old-fashioned tacked-down carpets and mattings, still so 
commonly used, must be done away with, unless an insecticide is used, 
which when applied to carpets in wetting quantities does not injure 




Fig. 180. — Two varieties of the com- 
mon "digger" ground squirrel of the 
Pacific Coast. The squirrel at left is 
the Douglas ground squirrel (Citellus 
dcuglasi) , found along the coast north 
of San Francisco Bay ; the one to the 
right is the California ground squirrel 
(Citellus beecheyi beecheyi), the com- 
mon ground squirrel of the interior 
valleys and a carrier of bubonic 
plague. (Photo by University of 
California Museum of Vertebrate 
Zoology.) X .16. 



FLEAS AND LOUSE FLIES 285 

the fabric. Benzine is often recommended, but its dangers must be 
considered, both before and after applying. The writer does not 
undertake the responsibility of recommending benzine for this 
purpose. With the removal of carpets and matting, floors can 
easily be moistened with an oil mop, using kerosene. All parts 
of the floor in all parts of the house must be reached. The 
odor of kerosene is not particularly disagreeable and at all events 
soon disappears. Treatment should be repeated at least once every 
three or four weeks during the flea season. This method of treatment 
has invariably given good results. Dr. L. O. Howard recommends a 
free sprinkling of pyrethrum powder as the easiest remedy to be applied, 
or washing the floors with hot soapsuds. Dr. Henry Skinner has 
successfully destroyed fleas in a badly infested room by sprinkling the 
floor liberally with about five pounds of flake naphthalene and closing 
the room for twenty-four hours. The acrid fumes destroyed the fleas 
and inflicted no material injury (Felt). 1 

(B) Treatment of dogs, cats and other domesticated animals kept in or 
near the house is essential to the control of fleas. Mats on which 
house pets sleep should be shaken out over kerosene, soapsuds or a 
fire every few days in order to destroy flea eggs which have fallen from 
the host when it shakes itself. The sleeping quarters should be liberally 
dusted with California buhach or pyrethrum powder. Fleas also breed 
abundantly in loose dry manure and debris in stables, chicken houses, 
yards, etc. A spray of high flash point fuel oil is very useful under these 
circumstances. The best method to keep cats, dogs, monkeys, etc., 
free from fleas is to give them frequent baths with warm water to which 
enough creolin is added to make a 2 per cent solution. If the animal 
is dipped in the solution, the eyes should be quickly rinsed or sponged 
with clear water. 

Animals infested with fleas may also be liberally dusted with Cali- 
fornia buhach or pyrethrum powder. The dust rubbed well into the 
hair causes the fleas to drop off in a stupefied condition, when they can 
be brushed up and burned. If the latter is not done the insects soon 
revive and go about their " business " as usual. 

(C) Rat Control. — Not only are rats an object of control because 
of their menace to health but they are also injurious in many other 
ways. According to Lantz 2 there are several species of house rats 
(Fig. 181), among them the black rat (Mus rattus), the roof rat (Mus 
alexandrinus) and the brown rat (Mus norvegicus), of which the last 
named species is by far the commonest. All of these species were 
imported from the Old World. The habits of house rats, except the 
roof rat, are generally quite similar, hence methods of control are alike 
applicable, and manifestly the control of the host involves the control 

1 Felt, E. P., 1909. Control of household insects. Museum Bull. 129. 
N. Y. State Museum, Albany, N. Y. 

2 Lantz, David E., 1909. How to destroy rats. U. S. Dept. of Agric, 
Farmers' Bull. 369. 



286 MEDICAL AND VETERINARY ENTOMOLOGY 

of the flea. Rucker * has well said, " Rodent extermination is a 
problem with difficulties arising from the animal's highly developed 
regard for self-preservation. In the main, the rat requires two condi- 
tions for life. He needs plentiful food and places suitable for nesting 
and breeding. Eliminate either of these elements and you drive away 
your rats. Yet the problem remains far more difficult than shown in 
the simple terms of the above equation. The fabulous speed at which 
rats multiply will baffle all but the most determined and efficient efforts 
to exterminate them. Under normal conditions each female bears three 
litters a year and each litter produces ten young. Under conditions 
ideally favorable it has been computed that one pair of rats will, in 




Fig. 181. — House rats, (a) Mus rattus, the black rat; (6) Mus norvegicus, the brown 
rat; (c) Mus alexandrinus , the roof rat. X .13. 



five years, provided all can live so long, increase to 940,369,969,152. 
Such a result is, of course, impossible in nature. . . . The size and 
frequency of rodent litters decreases proportionately with every cutting 
off of food supplies. Separate the rat from his pabulum and he will 
not breed so freely nor so often as when he is well fed. Destroy rat 
habitations and make it impossible for them to find new nesting places, 
and breeding will virtually cease, since the unsheltered progeny can no 
longer survive, and since the starving rats are driven to cannibalism in 
,the struggle for existence." 

Rat control may be accomplished by the proper combination of 
the following methods depending upon circumstances, (a) Rat proofing 
is by far the most important method. This is done by the use of con- 
crete in building foundations and floors to stables, corncribs, poultry 
houses, outbuildings, dwellings, etc. Cement construction requires 

1 Rucker, William Colby, 1910. "Rodent extermination" in U. S. Public 
Health Bull, on "The rat and its relation to the public health," pp. 153-162. 



FLEAS AND LOUSE FLIES 287 

comparatively little skill, is not expensive and is becoming an im- 
portant factor in building the rat out of existence, (b) Cutting off the 
food supply essentially means (1) proper disposal of garbage, i.e. by 
burning the same speedily or placing it in covered metal garbage cans ; 
(2) cremation of slaughter house refuse ; (3) use of heavy wire netting 
for the protection of foodstuffs, feed bins, etc. (c) Natural enemies 
of the rat where otherwise not objectionable should be protected. 
Among the hawks, the red-tailed species (Buteo borealw) is said to be 
most efficient ; among the owls, the barn owl (Aluco pratincold) is of 
greater importance ; skunks and weasels are good ratters ; a well- 
trained fox terrier is a very useful adjunct to every farm, (d) Rat 
trapping is best accomplished by means of the snap traps. These 
should be well smoked and baited with fried bacon securely tied to the 
trigger. Each time before using, it is well to scald the trap with hot 
water and " sizzle " the bait with a lighted match or torch, (e) Rat 
poisoning is ordinarily dangerous to the life of domesticated animals 
and children. Among the poisons commonly used are (1) phosphorus 
paste prepared by mixing crude phosphorus over heat with glucose, 
cheese, meat, etc. Danger from combustion must be borne in mind. 
(2) Arsenic paste consists of an arsenious acid (powdered white arsenic) 
combined with oatmeal, cheese, toast, etc. (3) Strychnine crystals 
(strychnine sulphate) may be placed in pieces of cheese or meat and 
put in the rat runways. Extreme caution must be exercised in the use 
of rat poisons owing to danger to human life. State laics must be regarded 
in this respect as well. 

(D) Squirrel Control. — The most destructive as well as most dan- 
gerous species (as referred to public health) are the " digger " ground 
squirrels of the genus Citellus (Fig. 180). These squirrels live in colonies, 
ordinarily, and dig an extensive meshwork of connecting burrows. Their 
food consists of grain, seeds and fruit and is stored for the winter. 
The young are usually born in March and April in California and their 
litters number from five to ten. Three general methods of control are 
commonly employed. (1) Shooting and trapping. Shot guns carry- 
ing No. 7 or 8 shot are best employed, and chain traps are the best if 
trapping is to be done at all. (2) Suffocation in the burrows may be 
accomplished by either flooding with water or by the introduction of 
poisonous gases. Carbon bisulphide is the most efficient agent and is 
commonly employed. The following account of this gas and its use is 
based largely on the work of Simpson. 1 

Carbon bisulphide is obtained commercially in the form of a liquid, 
which is readily vaporized or is converted chemically into other gases. 
While it is the most useful material as applied against ground squirrels 
there are some objectionable features, namely, it is very inflammable, 
must be kept in tightly closed containers and under certain conditions 

1 Simpson, F., 1911. Ground squirrel eradication. California State 
Board of Health BuUetin, No. 8, Vol. 6, pp. 507-512. 



288 MEDICAL AND VETERINARY ENTOMOLOGY 

may explode; furthermore during the dry season if " exploded " in the 
burrow there is danger of igniting dry grass or other inflammable ma- 
terial in the vicinity. If handled with as much care as gasoline, for 
example, the danger is not so great after all. The advantages in its 
use are, that it is readily converted into a poisonous gas, diffuses quickly, 
destroys life rapidly and can be used most readily during the rainy 
season when green food is abundant, thus preventing the most successful 
use of poisoned grain. 

The bisulphide may be used in one of two ways, namely, in the 
simple liquid condition by evaporation, when there will be but little 
waste, or it may be used by igniting or exploding it. In either case 
it is suggested that from one to three days prior to the application of 
the poison all squirrel burrows in the area to be treated should be stopped 
with earth. The holes found opened indicate the burrow in which 
there are squirrels. 

The method of applying the bisulphide by the ignition method is as 
follows : To handle a large area to best advantage two men working 
together is suggested. " One man is provided with a supply of ' waste/ 
' sacking,' or other absorbent material, divided into a number of small 
balls about half the size of the fist. The bisulphide is carried in an 
ordinary one gallon oil can, and refilled from time to time from a supply 
kept in a cool place out of the sun. He is supplied with matches. His 
' pardner ' carries a mattock or long-handled shovel. On arrival at 
an opened squirrel burrow, a ball of ' waste ' is saturated with two 
ounces of bisulphide, dropped deeply in the burrow and then a match 
applied. After a moment's time the man with the shovel stops with 
earth this burrow and all other burrows near from which the gas es- 
capes. On subsequent inspection of the field all opened burrows will 
indicate holes lacking effective treatment." Exploding the bisulphide 
thus causes considerable gas to escape, but " the ignition produces a 
violent chemical reaction and as a result sufficient oxygen from the air 
combines with the carbon and sulphur elements to produce a volume of 
gas three times that which the original bisulphide would produce on 
evaporation. The gases produced, carbon dioxide and sulphur dioxide 
in the proportion of 1 to 2, seem just as effective as bisulphide of carbon, 
and the method is superior in that the explosion produced drives these 
gases deeply into the burrow." Two ounces or 60 cc. of the bisulphide 
produces about twelve gallons of gas. 

To use the gas unexploded simply omit igniting it. 

A much cheaper and more efficient method of destruction with 
carbon bisulphide has been devised by Long * and others, namely, a 
pump with a device measuring the quantity of liquid, and serviceable 
at all seasons of the year. The pump loaded with nine pints of bisulphide 
weighs twenty-five pounds. Refined bisulphide should be used in this 

1 Long, John D., 1912. A squirrel destructor. U. S. Pub. Health Re- 
ports. No. 98. (Reprint.) 



FLEAS AND LOUSE FLIES 289 

pump because the metal is rapidly corroded by the crude material. 
The refined bisulphide is said to contain 99.92 per cent carbon bisulphide 
and 0.08 per cent sulphur in solution and no hydrogen sulphide nor 
sulphuric acid. 

Only one half ounce (15 cc.) is required for each hole against two 
ounces by the ignition method, and it is claimed that the men using the 
pump have been able to treat from 200 to 250 holes with each gallon 
of the bisulphide, against 50 to 60 holes per gallon with the waste ball 
method above described. The cost of the apparatus is about $10 per 
machine and the cost per acre of treatment, going over the ground 
twice, is estimated at 20 cents with ten squirrel holes per acre. 

The use of the apparatus is thus described (see Fig. 182) : " Insert 
the hose in the squirrel hole at least one foot ; then run one half ounce of 
bisulphide from the reservoir into the measuring cup ; then turn cock 
with handle down to allow liquid to run into vaporizing chamber, mean- 
while covering the hole with dirt with the aid of a mattock. Then 
pump thirty strokes (in cold weather use one ounce with forty strokes) . 
This equals 12 cubic feet or 1.5 per cent bisulphide gas. Withdraw 
the hose, close hole opening by stamping in the dirt with the heel and 
proceed to the next hole." 

(3) Squirrel Poisoning. — In the use of poison for squirrels several 
important factors must be considered, namely, it must not be distasteful 
to the rodents and must enter the circulation readily ; the poison must 
be applied to food readily eaten by the squirrels and at a time when 
the usual green food is at its minimum. It has been found that strychnia 
sulphate (the pure alkaloid should not be used) is most effective, but the 
bitter taste must in some manner be concealed. The use of whole 
barley, i.e. threshed but still retaining the husk, is recommended by 
the U. S. Biological Survey. In this form the barley is not eaten by 
birds and is most acceptable to the squirrels ; it is also cheaper in this 
form. Wheat is very acceptable to the rodents but when poisoned is 
very destructive to birds, particularly quail, doves and other grain eaters. 

Piper of the U. S. Biological Survey has devised a formula whereby 
the bitter taste of the strychnine is delayed about two minutes, thus 
enabling the squirrel to fill its cheek pouches before the bitter taste is 
noted, — the formula is as follows : 

Barley (recleaned) 18 pounds 

Strychnine sulphate 1 ounce 

Soda 1 ounce 

Saccharine 1 dram 

Thin soupy starch paste 1 pint 

Corn sirup (Karo or equal) 2 oz. 

Dissolve the strychnine in hot water; thicken with starch to thin 
soupy consistency. Mix the soda in | pint hot water ; stir into poisoned 
starch. When efferyescence ceases, add sirup and saccharine, apply to 
grain and continue mixing until mixed and dry. 



290 MEDICAL AND VETERINARY ENTOMOLOGY 




FLEAS AND LOUSE FLIES 291 

According to Simpson (loc. cit.) grain poisoned with strychnine 
placed in proper containers will retain its poisonous character and re- 
main effective for an indefinite period, but heavy dews and rain may 
remove the poison and destroy the efficiency of the grain in this respect. 
Therefore this method is applicable during the dry season only. The 
above author states that thirty kernels in the cheek pouches of squirrels 
rapidly prove effective, whereas sixty or ninety or more in the stomach 
may produce only a few convulsions and recovery ensues. He says, 
" This fact should be remembered in placing poison, for by scattering 
the grain a few kernels here and there near the burrow the squirrel is 
induced to store the grain temporarily in the cheek before a sufficient 
quantity is obtained for a meal. . . ." It should be scattered where 
the squirrel is accustomed to find food, and will probably be found most 
efficient if placed early in the morning, between the hours of 3 a.m. and 

7 A.M. 

The Chigoe Flea (Sarcopsylla penetrans Linn.), known as " jigger," 
" chigger," " chique," or " sand flea," is a tiny burrowing flea (Fig. 
183) found in the tropical and antitropical regions of North and South 
America, also in the West Indies and Africa. Its introduction into 
Africa is said to have occurred as late as 1872. The chigoe is a reddish 
brown flea about 1 mm. in length, 
except that the impregnated 
female may become as large as a 
small pea, the head is proportion- 
ately large, there are no ctenidia 
on the head and thorax, the palpi 
are four-segmented and the mouth 
parts are conspicuous. The adult 
fleas are intermittent feeders but 
adhere closely to the host, the 
female when impregnated proceeds 
to burrow into the skin of the 
host. The eggs are deposited 
either in the ulcer or drop to the 
ground when discharged from the 
body of the female. The larvae FlG 183 . _ The chigoe fleE) Der matophiiu S 
which emerge in a few days from penetrans, x 35. 

the eggs are typical flea larvae. 

Those hatching in the ulcer drop to the ground to develop under condi- 
tions similar to those having hatched on the ground. The larval period 
under favorable conditions probably requires not more than ten to four- 
teen days and the cocoon or pupal period about a like number of days. 

Pathogenesis. — The chigoes commonly attack the bare feet, these 
being nearest the ground, infesting the skin between the toes, and the 
soles ; no part of the body is really exempt from attack. The burrow- 
ing female flea causes extreme irritation, the area surrounding the flea 




292 MEDICAL AND VETERINARY ENTOMOLOGY 

becomes charged with pus, producing a distinct elevation. The ulcera- 
tions due to the presence of numerous chigoes become confluent and 
very grave results are often involved. Wellman attributes the com- 
monly observed auto-amputation of toes to the work of the chigoe. 

Treatment and Control. — Where the chigoe flea commonly occurs, 
the habitations of humans and of domesticated animals (for these are 
also subject to attack) must be kept clean and free from dust, the floors 
may be swept up with a liberal sprinkling of naphthalene flakes, or with 
fresh buhach or pyrethrum powder. Where possible, kerosene treatment 
should be applied as described above for other fleas. Walking in bare 
feet should be avoided. 

Parts of the body attacked by the fleas should receive immediate 
attention. The insect can be removed quite easily by means of a sterile 
needle or very fine pointed knife blade. The wounds caused by this 
treatment are then carefully dressed and allowed to heal. Applications 
of turpentine or other remedies serve to kill the fleas, which are then 
discharged by ulceration. 

The Hen Flea, Echidnophaga (Xestopsylla) gallinacea, also known 
as the " stick tight " of poultry, is one of the worst poultry pests in 

many parts of subtropical America 

(Fig. 184). It commonly attacks 

^g|^^ poultry of all kinds, cats, dogs, 

d| H^ horses and even humans. Osborn 

4S Sk (Joe. cit.) states that this species 

9 INHr differs from the foregoing " in having 

HLrf the hind angles of the metathoracic 

scales angled instead of rounded 

4 and the eyes and antennae in the 

posterior half of the head. It is 

from 1 to 1\ mm. in length." 

Before copulation both sexes 
are active, hopping about much as 
do other species of fleas. Shortly 

Fig. 184. -Echidnophaga gallinacev, the af ter , *«*&* be Sj nS , the females 

chicken flea or stick tight, x 25. attach themselves firmly to the skin 

of the host and begin to burrow. 
At this time the sexes are in copulation. The burrowing females 
deposit their eggs in the ulcers which have been produced by the in- 
festation. The larvas crawl out of the ulcer and drop to the ground, 
where they grow rapidly, under favorable conditions, feeding on ni- 
trogenous matter, dry droppings, etc. The full-grown larva, which 
is not unlike other flea larvae, is about 4 mm. in length, having reached 
this stage in evidently about two weeks. The larva then spins a. 
cocoon, pupates and in about two weeks emerges as a full-developed 
flea. The life history requires about four weeks, more or less, based 
on rather crude observations. The writer believes also that eggs. 



FLEAS AND LOUSE FLIES 293 

are deposited in the dust or dry droppings of poultry, or in old nests, 
etc. 

The fleas are most likely to attack the skin around the eyes or the 
anus or other bare spots. The ulceration and wart-like elevations 
around the eyes often become so aggravated that blindness results, 
the host is unable to find its food and death results. 

To control the hen flea a thorough cleaning up is very necessary. 
The debris, dust, etc., must either be burnt or treated liberally with 
kerosene right in the yard so that the fleas do not become distributed 
while carrying away the refuse. The writer recommends that the yards 
and coops, particularly crevices, be thoroughly scalded out by liberal 
applications of boiling water or by the use of kerosene or a light fuel oil 
applied with a spray pump. Coops and yards which have crude oil 
floors are comparatively free from fleas and other parasites if otherwise 
kept in good condition. The hot water or oil treatment must be re- 
peated once every three or four weeks during the flea season. The use 
of sheep dips, carbolic acid sprays, etc., does not, as a rule, give good 
results in controlling chicken fleas. 

In addition to the above treatment infested chickens must also receive 
attention in order to destroy the ovulating female fleas. This may be 
done by dipping the birds in a 5 per cent solution of Zenoleum, Kreso 
or even Creolin. The use of naphthalene flakes in the nests is recom- 
mended or if this seems undesirable a liberal layer of slaked lime in the 
bottom of the nest may be substituted. 

B. Louse Flies and Forest Flies 
Order Diptera, Family Hippoboscidce 

Characteristics of Hippoboscidae. — The family Hippoboscidse is 
characterized by Williston as follows : " Head flattened, usually at- 
tached to an emargination of the thorax ; face short ; palpi wanting ; 
antennae inserted in pits or depressions near the border of the mouth ; 
apparently one jointed, with or without a terminal bristle or long hairs. 
Eyes round or oval, sometimes very small; ocelli present or absent. 
Thorax flattened, leathery in appearance ; scutellum broad and short. 
Halteres small or rudimentary. Abdomen sac-like, leathery in appear- 
ance, the sutures indistinct, legs short and strong, broadly separated 
by the sternum; tarsi short; claws usually strong and dentated; 
empodia usually present. Wings present or absent. . . . They are 
all parasitic in the adult stage upon birds or mammals. The larvae are 
pupiparous, but pass nearly the whole of this stage within the abdomen 
of the parent, being extruded when nearly ready to transform into the 
mature fly." The mouth parts are tubular and are fitted for sucking 
blood. The species occurring on birds are included in the genera 
Olfersia and Ornithomyia, which according to Osborn are distinguished 



294 MEDICAL AND VETERINARY ENTOMOLOGY 




in that the former has two teeth under each claw and has no ocelli. 
The most important species is the sheep tick or sheep louse fly, Melopha- 
gus ovinus Linn. 

The Sheep " Tick," Melophagus ovinus Linn. (Fig. 185), is a wingless 
species, reddish brown in color, about 5-7 mm. in length. The head is 
short and sunken into the thorax, the body is sac-like, leathery and spiny. 
Life History. — The young of the sheep tick leave the body of the 
female ready to pupate. The extruded pupa (Fig. 185) during the 
course of a few hours becomes chestnut-brown in color, the secretion 
with which it is covered hardens and serves to glue the pupa firmly 

to the wool of the sheep. The 
pupse are commonly found on in- 
fested sheep in the region of the 
shoulders, thighs and belly. Pupae 
may be found on sheep at all times 
of the year, though the time re- 
quired for development in the win- 
ter is longer than in the summer. 
Swingle x who has carried on most 
careful observations on this insect 
states that pupa? require from nine- 
teen to twenty-three days to hatch 
in the summer, whereas nineteen to 
thirty-six days are required during 
the winter on sheep kept in the 
barn and probably forty to forty-five 
days on sheep out of doors. The time required for the females to reach 
sexual maturity is from fourteen to thirty days and over, when they 
begin extruding young at the rate of one about every seven or eight 
days. Swingle regards about four months as the average life of a sheep 
tick and that from 10 to 12 pupse are deposited on an average. 

The whole life of the tick is spent on the host ; when off the sheep 
the insects die in from two to eight days, most of them dying in about 
four days. 

Pathogenesis. — The presence of a few louse flies on the bodies of 
sheep does not materially affect them. Ordinarily the presence of the 
insect is indicated by the fact that the animal rubs itself vigorously, 
bites the wool and scratches. Badly infested animals show emaciation 
and general unthriftiness. 

Control. — ■ Since the principal time for migration from the sheep 
to the lambs is at shearing when the insects are taken off the hosts with 
the wool, it is wise to take particular pains at this time to store the wool 
at some distance from the lambs. Inasmuch as the ticks die within a 
week when away from the host, and cannot well crawl any great dis- 

1 Swingle, Leroy D., 1913. The life history of the sheep-tick, Melopha- 
gus ovinus. Univ. of Wyoming Agr. Exp. Sta. Bull. No. 99. 



Fig. 185. — The sheep tick or louse fly, 
Melophagus ovinus. Pupa (left) , adult 
(right). X 4.5. 



FLEAS AND LOUSE FLIES 



295 



tance, the above suggestion is well worth considering. Swingle states 
that " a sheep free from ticks can be kept for months beside a heavily 
infested one with a tight partition only three feet high between them 
without becoming infested. ... A bunch of females placed in the 
wool of a sheep will be found in practically the same place for two days. 
Males, however, are more inclined to migrate." A flock of sheep once 
freed from ticks can therefore be kept clean unless infested animals are 
introduced. 

The writer has reasons to doubt the efficiency of the usual sheep dips 
such as " lime and sulphur M and tobacco decoctions in the destruction 
of the sheep tick, however, other dips, such as Kreso, Zenoleum and 
Chloronaphtholeum, if used as directed for sheep scab mites will kill the 
" ticks " but not the pupae. The time for the second dipping is governed 
by the life history of the parasite, hence in warm weather (dipping for 
ticks is best done in the autumn), the second dipping should take 
place in about twenty-four days after the first. 

Xo doubt a liberal use of buhach or pyrethrum powder, particularly 
as a winter treatment, would prove beneficial. 

The louse fly of the deer is Lipopiena depressa Say (Fig. 186), an 
exceedingly common parasite of the deer. This species is smaller than 
Melophagus ovinus, other- 
wise similar ; it is wingless 
when found on the host, 
but has well-developed 
filmy wings which are 
evidently lost later on 
(Fig. 186). These para- 
sites have been found in 
chains, three or four at- 
tached to each other, the 
first tick drawing blood 
from the host, the second 
with its proboscis thrust 
into the abdomen (dor- 
sallyj of the first, the third drawing on the second and so on to the 
last most lucky individual. 

The forest fly or louse fly of the horse is Hippobosca equina Linn. 
This species is quite large ( length S mm.), is winged and a fairly good 
flier. It is common in many parts of the world but occurs rather in- 
frequently in America. The damage which it does would depend en- 
tirelv on its abundance. 




Fig. 186. — Louse fly of the deer, or deer tick (Lipop- 
tena depressa), showing wingless and winged form. 
X 5. 



CHAPTER XVIII 



THE TICKS 



Class Arachnida, Order Acarina, Superfamily Ixodoidea 

Characteristics of Arachnida. — The general characteristics of the 
class Arachnida have already been pointed out in an earlier chapter, 
but it is in place to refer to these once more. In the arachnids the 
adults always have four pairs of legs (the larvae are commonly hexapod), 
wings are absent as are antennae and compound eyes. Simple eyes 
may be present or absent ; when present they are often more than two 
in number. The mouth parts usually consist of a pair of piercing 
chelicerae. The respiratory organ in some arachnids, for example 
spiders, is called a " lung book " ; in many species however, particularly 
ticks, there is present a well-defined tracheal breathing system. The 
body is commonly divided into two parts, — cephalothorax and ab- 
domen, the former bearing the walking appendages. In many species, 
for example, the ticks and mites, the regions 
of the body are fused. The sexes are distinct 
and there is often marked sexual dimorphism. 

Order Acarina. — To the order Acarina be- 
long the ticks and mites. The cephalothorax 
and abdomen are fused, the larvae have only 
three pairs of legs; the eyes in the parasitic 
forms are either very small or entirely wanting. 
The members of this group are never large, 
some ticks may be 15-16 mm. in length, while 
many of the mites are barely visible to the 
naked eye. 

The Ticks. — The ticks are acari varying in 
size from 1 mm. in the seed tick or larval stage 
to about 15 mm. in the fully engorged mature 
female of several species. They are found in 
all parts of the world and are commonly re- 
garded as pests of domesticated animals and frequently attack man. 
The ticks belong to the superfamily Ixodoidea. They are blood- 
sucking arachnid parasites, body covered with a leathery, more or less 
glossy cuticle, the head or capitulum consisting of characteristic pro- 

296 




Fig. 187. — Capitulum of 
a tick (larval Argas) , ven- 
tral aspect, showing (1) 
basis capituli ; (2) palpi ; 
(3) hypostome ; (4) che- 
licerae ; (5) hood or sheath 
of chelicerse ; (6) denticles 
of chelicerse. (Drawing 
by W. L. Chandler.) 



THE TICKS 297 

trusible chelicerse and a serrate hypostome (Fig. 187). The females 
are capable of very great distention, having the appearance of a seed 
rather than that of an insect. 

Life History. — The life histories of ticks vary considerably for the 
several species, hence it is quite impossible to generalize, except that 
it may be said that all species of ticks, with very few exceptions, pass 
through four stages, — egg, seed tick, nymph and adult and that from six 
weeks to over six months are required to pass through these four stages. 
Eggs are deposited by the fully engorged females, the number varying 
from 100 in some species to 5000 and over in others. The newly hatched 
larva?, known as seed ticks, are hexapod (six-legged) and remain in this 
condition until the first molt. The nymph emerges from the first 
molt with its fourth pair of legs present, and remains in this stage 
until the second molt, after which the adult tick emerges ; often a third 
or even a fourth molt or more takes place before the adult stage is 
reached. Copulation takes place after the last molt, when the females 
engorge and then deposit eggs. In the majority of species, the ticks 
drop off the host animal to molt, but in several species, notably the 
Texas cattle fever tick (Margaropus annulatus), the molting takes 
place on the host. Eggs are invariably deposited on the ground by 
the fully engorged females. There may be two or possibly three genera- 
tions of ticks in one year under very favorable climatic conditions in 
such species as molt on the host. 

The seed ticks emerging from the eggs on the ground commonly 
climb up grasses and other low vegetation, thus coming in easy reach 
of grazing or passing animals. The nymphs employ the same method. 

Tick Mouth Parts. — ■ The capitulum or head bears the mouth parts 
and accessory external structures (Fig. 187). The basal portion is 
known as the basis capituli, from which projects forward and dorsally a 
pair of protrusible cheliceroe. The distal portions (digits) of the chelicerse 
are divergent and provided with recurved teeth. Projecting forward 
and situated ventrally and median on the basis capituli is the hypostome 
bearing many recurved teeth. Laterally are located the palpi (one pair) , 
consisting of four articles, of which two or more may be fused, — com- 
monly only three are visible. 

Feeding Habits. — When sucking blood both the hypostome and 
the chelicerse are inserted into the tissue of the host. Because of the 
recurved teeth the tick is enabled to hold so fast to the host that it is 
difficult to remove it without tearing the capitulum from the body of 
the tick. The tick itself, however, withdraws its mouth parts quickly 
and apparently with little effort by slipping the hoodlike portions of the 
capitulum over the relaxed mouth parts and by means of a quick jerk 
drops off and escapes. 

The length of time that a tick remains attached in the act of feeding 
depends entirely on the species and the stage of development. The 
seed ticks commonly feed for a number of days ; the nymphs and adults 



298 MEDICAL AND VETERINARY ENTOMOLOGY 

differ greatly in this respect, — thus the common poultry tick (Argas 
persicus) feeds nightly and intermittently, while the nymphs and adults 
of the cattle tick (Margaropus annulatus) feed from six to eight 
days before becoming engorged. Other species of ticks, notably the 
Pajaroello (Ornithodorus coriaceus), engorge themselves fully in from 
fifteen to twenty-five minutes. 

Longevity. — The longevity and hardiness of ticks is something 
truly remarkable, a matter not to be overlooked in control measures, 
particularly pasture rotation in which starvation is the principal factor. 
Furthermore, fluids which destroy the life of most insects in a few 
minutes act very slowly on these arachnids, for example, immersion in 
70 per cent alcohol will not kill the ticks for hours and xylol is resisted 
for about half an hour. The writer has found the poultry tick Argas 
persicus particularly resistant. 

Unfed larval ticks of the above species remain alive quite readily 
for a month and would probably survive longer if kept in a moist cham- 
ber. Nymphs survive a longer time and the adults even longer than 
the nymphs. Nuttall : cites cases in which nymphs of this species 
survived two months, and adults (unfed) "a little over two years." Gray- 
bill 2 reports considerable variation in the longevity of the Texas fever 
tick, depending on the season of the year; unfed larvae survived 
from 7 to 85 days (aver. 38.6) for July, and 30 to 234 days (aver. 167.4) 
for October. Nuttall 3 cites cases in which the larva? of Ixodes ricinus 
survived 19 months, unfed nymphs 18 months and unfed adults 15 to 
27 months. 

Major Divisions (classification). — All ticks (superfamily Ixodoidea) 
are commonly divided into two families, viz. : Argasidse (also referred 
to as subfamily Argasinse) and Ixodidse (also referred to as subfamily 
Ixodinse). The presence of a scutum (or shield) located dorsally imme- 
diately posterior to the capitulum in the Ixodidse is the most striking 
differential character. This character is absent in the Argasidse. 

The following table, on page 300, adapted after Nuttall (1908, 
loc. tit.), will be found useful in separating the two families. (See 
also Fig. 188.) 

1 Nuttall, G. H. F., and Warburton, Cecil, 1908. Ticks, a monograph of 
the Ixodoidea, Part I, Argasidae. pp. x + 104 + 35. Cambridge (England), 
Univ. Press. 

2 Graybill, H. W., 1911. Studies on the biology of the Texas fever tick. 
U. S. Dep. of Agric, Bur. Animal Ind. Bull. 130. 

3 Nuttall, G. H. F., and Warburton, Cecil, 1911. Ticks, a monograph of 
the Ixodoidea. Part II, Ixodidse. pp. xix + 105 + 348. Cambridge, 
(England), Univ. Press. 



THE TICKS 



299 



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300 MEDICAL AND VETERINARY ENTOMOLOGY 



TABLE XXI 

Differences by Which the Two Families of the Ixodoidea may 
be Separated. (Adapted after Nuttall) 



Sexual dimorphism 
Capitulum 

Base 

Palpi 



Body 



Legi 



Scutum 

Festoons 

Eyes (when present) 

Coxae 
Tarsi 
Pulvilli 



ARGASID.E 



Slight 
Ventral 

No porose areas 
Leg-like, with subequal 
articles 

Absent 
Absent 

Lateral on supracoxal 
folds 

Unarmed 

Without ventral spurs 

Absent or rudimentary 



IXODID-E 



Marked 
Anterior 

Porose areas in 9 
Relatively rigid, of very 
varied form 

Present 

Generally present 
Dorsal on the sides of 
the scutum 

Generally armed with 

spurs 
Generally armed with 1 

or 2 ventral spurs 
Always present 



The Ixodine Ticks 
The Texas Cattle Fever Tick 



The Texas Cattle Fever Tick (Margaropus annulatus Say = Bodphilus 
bovis Riley) is economically considered the most important species of 
the family Ixodidse (Fig. 189). It is restricted to North America, where 
it occurs south of the Mason and Dixon line. It is typically a cattle 

tick, although it occurs at times in 
smaller numbers on deer, sheep 
and other animals. 

Fully engorged females range 
in length from 10 to 12 mm., while 
the males range from 3 to 4 mm. 
The body of the female is about 
equally rounded both posteriorly 
and anteriorly with slight median 
incurving. The anterior pair of 
legs is set well out on the shoul- 
ders away from the capitulum (in 
Dermacentor close to the capit- 
ulum). The palpi are very short 




Fig. 189. — The Texas fever tick, Marga- 
ropus annulatus ; female (left) and male 
(right). X 3.5. 



THE TICKS 301 

and stalky, so that the entire capitulum or head is inconspicuous. 
The relatively small (1+ mm. long) scutum or shield is solid chest- 
nut brown in color. This is commonly the only species of tick 
in some localities with a chestnut-brown scutum. Two other species 
of ticks with a chestnut-colored scutum occur occasionally with the 
Texas fever tick, namely the " Lone Star Tick," Amblyomma amer- 
icanum, which has, however, a distinct silver white circular spot 
at the posterior end of the scutum, and Ixodes ricinus and its varieties, 
e.g. Ixodes calif ornicus, in which the capitulum is long, and the anterior 
pair of legs are attached close to it. Other technical diagnostic details 
are of course present in the latter two species. 

The stigmal plates of M. annulatus are nearly circular ; the porose 
areas are elliptical and far apart. 

Economic Importance. — It has been estimated l that the annual 
losses to the South (U.S.) occasioned by the "cattle tick" directly and 
indirectly prior to 1906 amounted to S130,500,000. These losses are 
summed up as follows : 

" 1. Death, from Texas fever, of pure bred cattle imported from the 
North for breeding purposes. 

" 2. Death, from Texas fever, when cattle reared in isolated tick- 
free areas are unintentionally or accidentally placed with ticky cattle, 
or on tick-infested areas. 

"3. Death of native cattle from excessive parasitism and fever, 
occasioned by the ticks. 

" 4. Universal loss of weight by all tick-infested cattle, and their 
failure to gain flesh at a rate great enough to make beef production 
profitable. 

" 5. The lower price which " Southern " cattle bring upon the 
market, regardless of bow perfect their condition may be. 

" 6. Sterility induced in high-grade cattle by tick infestation. 

" 7. The expense of maintaining the Federal quarantine for the 
protection of the North against invasion by the tick, and the added 
expense of maintaining quarantine pens for Southern cattle shipped 
north for slaughter. 

"8. The discouraging effect on the breeding of pure bred cattle in 
the South by reason of Southern breeders not being allowed to exhibit 
in Northern show rings. 

" 9. By no means least, the potential loss in fertility of Southern 
farm lands due to a one-crop system which, with the tick eradicated, 
would quickly give way to a diversified agriculture which would con- 
serve and increase the fertility of our soils." 

Life History of Texas Fever Tick. — Most careful observations on 
the biology of the Texas fever tick have been made by the Bureau of 
Animal Industry of the U. S. Department of Agriculture and the fol- 

1 State Crop Post Commission of Louisiana, 1906. Circ. No. 10, "The 
cattle tick." 



302 MEDICAL AND VETERINARY ENTOMOLOGY 

lowing data is adapted after Graybill (1911, he. cit.). The maximum 
number of eggs deposited by a female tick according to this author was 
5105, minimum 357, with an average ranging from 1811 to 4089. 
The period of oviposition, time during which female deposits eggs, 
ranged from an average of 8.3 days for June (1907) to 127.5 days for 
November. The maximum period was 152 days and the minimum 3 
days, depending on temperature mainly. The incubation period, also 
dependent on temperature, ranged from 19 days in summer to 180 days 
in the early autumn, with the average of 43.6 days for April, 26.3 days 
for May, 24.5 days for June, 20.5 days for July, 21.2 days for August 
and 35.9 days for September. The hatching period depends on the 
time when the eggs are laid, the eggs first deposited ordinarily hatching 
first. The average period ranged from 10.6 days for July to 36 days 
for October, with a maximum period of 49 days and a minimum of 4 
days. The time during which the seed ticks remain alive, i.e. longevity 
of the newly hatched ticks, again varies considerably, depending on tem- 




Fig. 190. — Eggs (left), larva (right), of the Texas fever tick, Margaropus annulatus. 

X 50. 

perature; the longevity for April was found to be 65.1 days, May 62.3 
days, June 65.1 days, July 38.6, August 84.9 days, October 167.4 days. 
The total average time for the non-parasitic period ranged from 86.9 
days for June to 279.6 for October. 

The three stages (Fig. 190) considered in the parasitic period of the 
ticks are larval (seed tick), nymphal and adult. As Graybill has well 
said, " The duration of each of these stages and the duration of a single 
infestation upon cattle during different portions of the year are of great 
practical importance. Upon the duration of an infestation depends 
the time animals must be kept on the tick-free fields in order to become 
free from ticks." This author has found that after the seed tick has 
attached itself to the host the minimum larval period ranges from five 
to seven days, the minimum nymphal period of females from nine to 
thirty days, and the adult from five to thirty-three days, with a 




THE TICKS 



303 



total period of infestation, including the time for molting twice, which 
is accomplished on the host, at from thirty to sixty-six days. 

The more striking differences between the life histories and a com- 
parison of the life cycle of the Texas fever tick and the common dog 
tick (Dermacentor electus) are shown in the following two tables (Tables 
XXII and XXIII), adapted after Cotton: 1 

TABLE XXII 

Comparison of the Length of the Life Cycle of the Dog Tick and 
of the North American Fever Tick in Summer 

(After Cotton, he. cit, 1908) 



Dog Tics 
{Dermacentor sp.) 



North American Fever Tick 
(Margaropus annulatus) 



I. Adult tick becomes engorged on 
host animal and drops to 
ground 



II. Engorged tick begins egg laying 
(3000 ± eggs) after 3-5 days 



III. Seed ticks hatch from eggs in 
about 30 davs 



IV. Seed ticks bunch on grass and 
await coming of host animal, 
from one day to several weeks 



Adult tick becomes engorged on host 
animal and drops to ground 



Adult tick begins egg laying (3000 ± 
eggs) after 3-5 days 



Seed ticks hatch from eggs in about 
30 davs 



Seed ticks bunch on grass and await 
coming of host animal from one day 
to several weeks 



V. After feeding 7-12 days seed 
ticks drop to ground and 
molt 



VI. Ticks crawl up on grass and 
await coming of second host 
animal from one day to 
several weeks 



VII. Ticks get on second host animal 
and feed 5-10 days, then drop 
to ground and molt second 
time 



VIII. Ticks crawl up on grass and 

await coming of third host 

animal from one day to 
several weeks 



.After feeding 7-12 days seed ticks 
molt on host animal 



Ticks feed 5-10 days, then molt on 
host animal and mate 



IX. Adult ticks mate and feed 5-8 Adult ticks feed 4-14 days then drop 
days, then drop to the ground ! to the ground and lay eggs 
and lay eggs 



1 Cotton, E. C, 1908. Tick eradication. Agr. Exp. Sta. of the Univ. of 
Tennessee Bull. 81. 



304 MEDICAL AND VETERINARY ENTOMOLOGY 



TABLE XXIII 

Showing Prominent Differences between the Life Histories of the 
Dog Tick and the North American Fever Tick 



(After Cotton, loc. cit, 1908) 



Dog Tick 
(Dermacentor sp.) 


Nokth American Fever Tick 
(Margaropus annulatus) 


Leaves host animal for each molt 


Never voluntarily leaves host animal 
from attachment as a seed tick until 
fully mature 


Requires three separate host animals or 
may get on same host three times 


Requires but one host animal to reach 
maturity and gets on this one 
animal but once 


Can develop on a large number of dif- 
ferent kinds of animals 


Must find cow, horse, mule (deer or 
sheep) as a host animal or perish 


Does not transmit Texas fever 


Only natural means of transmission of 
Texas fever from one cow to another 


Usually requires a whole year to com- 
plete its life cycle, from egg through 
seed tick, nymph, and adult, to egg 
again 


Is able to complete its life cycle in 
about 60 days, thus allowing for 
three generations in one year, pro- 
vided hosts are available 


Because of the habit of dropping to the 
ground at each molt the parasitic 
and non-parasitic periods intermingle 
and therefore the life cycle cannot be 
divided into two distinct parts 


Life cycle is divided into two separate 
and distinct parts ; parasitic, passed 
on the host animal, and non-parasitic, 
passed off the host animal 


The habit of dropping to the ground for 
each molt materially reduces the 
chances of the seed ticks of this 
species reaching maturity 


The habit of remaining on the host 
animal until maturity renders it 
almost certain that every seed tick 
of this species finding attachment 
will reproduce itself 


Since the species has but one generation 
per year the progeny of one adult tick 
will produce 1,050,000 eggs in a single 
season 


Since this species has three generations 
per year the progeny of one adult tick 
will produce 5,825,036,452,578,000 
eggs in a single season 



THE TICKS 305 

Piroplasmosis applies to a group of diseases traceable to the Pro- 
tozoon genus Babesia (Piroplasma) , and related genera such as Theileria, 
Nuttalia, etc., belonging to the subphylum Sporozoa, class Telosporida, 
subclass Hsemosporida, order Xenosporida. The genus Babesia com- 
prises pear-shaped (varying somewhat to oval), red blood-cell inhabiting 
parasites (Fig. 191). Unlike the Plasmodia there is little or no pigment, 
and multiplication is by division in twos. Ticks are the usual carriers in 
which there is hereditary transmission from the female tick to the egg, 
and thus to the larva and nymph which act as the infecting agents. 
The most important example of Piroplasmosis is Texas cattle fever. 

Texas Cattle Fever. — Babesia (Piroplasma) bigemina, Smith and 
Kilbourne is the causative organism of Texas cattle fever, also vari- 
ously known as red water, splenic fever, tick fever, etc. The dis- 
ease is widely distributed, being endemic in southern Europe, Central 
and South America, parts of Africa, Mexico, the Philippines, and the 

southern United States where it has been 
known for more than a century, having 
been introduced into this country probably 
from Europe. 

The name Texas fever became attached 
to the disease because of the large herds of 
cattle which were driven northward from 
Texas and gave a certain disease in some 
mysterious manner to Northern cattle that 
crossed the trail of the Southern cattle. The 
Fig. 191. —Babesia bigemina nr st account of the disease was given by 
(Piroplasma bovis), showing James Mease in 1814 before the Philadelphia 

three stages in intracorpus- p, • , e -r, , . » ,, T innn 

cuiar development, x 2000. Society tor Promoting Agriculture. In 18/ 9, 

Salmon began an investigation of the dis- 
ease; and in 1889, Theobald Smith made his epoch-making discovery 
of the intracorpuscular protozoan parasite inhabiting the blood of the 
diseased cattle. Immediately thereupon followed the experiments of 
Kilbourne, on suggestion of Salmon, which proved the disease to be 
tick-borne, a suspicion held as early as 1869 according to Smith and 
Kilbourne. Until that time (1889) infection was variously attributed 
to saliva, urine or feces. 

The disease may assume either an acute or chronic form, the acute 
occurring during the summer months and the chronic during the autumn 
and early winter. The symptoms x of the acute form are as follows : 
The temperature often registers 106° to 108° F. within forty-eight hours 
after the first symptoms are noticed. The sick animal leaves the herd, 
stands with arched back and ears drooping, the muzzle dry, appetite 
lost and rumination stopped. There is constipation during the first 
stage of the disease, which may give way to diarrhea later. The manure 

1 Adapted largely after the description of L. L. Lewis, 1908. Texas fever. 
Okla. Agr. Exp. Sta. Bull. No. 81. 




306 MEDICAL AND VETERINARY ENTOMOLOGY 

is frequently stained with bile and may be tinged with bloody mucus ; 
the urine is often very dark red or coffee-colored. The blood becomes 
thin and watery, so that by making an incision into the tip of the ear 
and allowing the blood to flow over the hand it does not stick to the 
hand as does the blood from a healthy animal. 

Vast numbers of red blood corpuscles are destroyed by the para- 
sites, which accounts in a measure for the reddish color of the urine 
through the elimination of hsemaglobin by the kidneys ; and it is believed 
that the excessive work that the liver has to perform in attempting to 
transform the excess of destroyed corpuscles into bile, causes this organ 
to become deranged in function, and eventually a complete stagnation 
may result with fatal termination. Mortality ranges from fifty to 
seventy-five per cent. 

The chronic form of the disease is often hardly noticeable. The 
following comment by Lewis (Joe. cit.) is significant : " This is the type 
of fever usually seen among Southern cattle. Death does not occur as 
a rule, but the loss in growth and general condition is such as to make 
this type of disease very important. It is this loss in growth and con- 
dition rather than an actual numerical loss by death that constitutes 
the great damage suffered by the stock industry of the South. " 

Babesia bigemina (Piroplasma (bovis) bigeminum), the causa- 
tive protozoan parasite of Texas cattle fever, was discovered by 
Theobald Smith in 1889 and w T as called Pyrosoma bigeminum. The 
parasite (Fig. 191) is described by Smith and Kilbourne 1 as follows : 
" When blood is drawn from the skin during the fever, and examined 
at once with high powers (500 to 1000 diameters . . .) certain cor- 
puscles will be found containing two pale bodies of a pyriform outline. 
One end of each body is round and the body tapers gradually to a point 
at the other. They vary somewhat in size in different cases, but the 
two bodies in the same corpuscle are as a rule of the same size. They 
are from 2 to 4 ft in length and 1.5 to 2 /^ in width at the widest por- 
tion. Their tapering ends are directed toward each other and usually 
close together ; their rounded broad ends may occupy various positions 
with reference to each other. They may be seen together with the 
axes of the bodies nearly parallel or they may be far apart, the axes 
forming a straight line. The bodies themselves have a homogeneous, 
pale appearance, contrasting markedly with the inclosing red corpuscles 
from which they are sharply outlined. There is no differentiation into 
peripheral and central zone, no granular appearance of the body. . . . 
When exposed to a temperature of 35° C. to 42° C. on the warm stage 
some of these bodies, by no means all, exhibited changes of outline. 
These may go on continuously in some bodies, in others quite slowly. 
The motion most frequently exhibited consists not so much of a thrust- 

1 Smith, T., and Kilbourne, F. L., 1893. Investigations into the nature, 
causation and prevention of Texas or Southern cattle fever. U. S. Dept. of 
Agric, Bur. Animal Ind. Bull. No. 1, 301 pp. 



THE TICKS 307 

ing out and withdrawing of pseudopodia as of a continual recasting of 
the general outline of the body as we find it, for example, in the leuco- 
cytes of mammalian blood. . . . The number of infected corpuscles 
circulating in the blood during the high fever is usually quite small . . . 
from half to one per cent is near the truth in most cases. . . . Toward 
the fatal termination, there may be from 5 to 10 per cent of the cor- 
puscles with the pyriform parasites present." 

In 1888 an " investigation into the nature, causation and preven- 
tion " of the disease was undertaken by the United States Department 
of Agriculture, Bureau of Animal Industry, under the direction of Dr. 
D. E. Salmon. The work was done by Dr. Theobald Smith and Dr. 
F. L. Kilbourne and marks a most important epoch in our knowledge 
of protozoan diseases and in preventive medicine. 

During a period of about four years of nearly continuous investi- 
gation, the problem was exhaustively studied in both the field and in 
the laboratory. The field experiments were carried along three different 
lines, viz. : " (1) Ticks were carefully picked from Southern animals 
so that none could mature and infect the ground. The object of this 
group of experiments was to find out if the disease could be conveyed 
from Southern to Northern stock on the same inclosure without the 
intervention of ticks. (2) Fields were infected by matured ticks and 
susceptible cattle placed on them to determine whether Texas fever 
could be produced without the presence of Southern cattle. (3) Sus- 
ceptible Northern cattle were infected by placing on them young ticks 
hatched artificially, i.e. in closed dishes in the laboratory " (Smith 
and Kilbourne, 1893, he. cit.). 

Healthy native cattle (Washington, D.C.) were exposed to sick 
native cattle free from ticks for months without contracting the dis- 
ease, proving that the excretions had nothing to do with the trans- 
mission of the disease. In the absence of ticks, sick animals are harm- 
less. Again several thousand, mostly full-grown ticks, collected from 
cattle in North Carolina, were scattered over the ground in a field on 
September 13. Four native cattle were placed in the field Sept. 14; 
of these animals three contracted Texas fever. This experiment was 
repeated with five experimental animals, and a new-born calf, all of 
which contracted the fever. A yearling heifer was placed in a box 
stall and a number of young ticks, hatched artificially in glass dishes, 
were placed on the animal at intervals. The heifer contracted Texas 
fever. A repetition of this experiment on various occasions always 
gave similar results. It was definitely concluded that " Texas fever in 
nature is transmitted from cattle which come from the permanently 
infected territory to cattle outside this territory by the cattle tick 
(Boophilus bovis = Margaropus annulatus) and that the infection 
is carried by the progeny of the ticks which matured on infected cattle, 
and is inoculated by them directly into the blood of susceptible cattle." 

Just how the young tick becomes infected from the parent tick is 



308 MEDICAL AND VETERINARY ENTOMOLOGY 

still a question, but it seems reasonable to conclude that the protozoon 
migrates from the intestine of the parent, possibly in a manner similar 
to the development of the malaria parasite, eventually infecting the 
ovaries instead of the salivary glands as in the mosquito, and thus 
the ova become infected before ovulation and the newly emerged 
seed tick is consequently infective. The authors above cited state 
that the contents of the bodies of ticks in various stages of growth 
were examined microscopically with considerable care, but that the 
abundant particles resulting from the breaking up of the ingested blood 
corpuscles obscured the search so that nothing definite was discovered. 
" The very minute size of the microorganism renders its identification 
well-nigh impossible, and any attempt will be fraught with great diffi- 
culties." 

Other tick carriers of the protozoon are Boophilus australis Fuller 
and B. decoloratus Koch within their range. 

Controlling the Texas Fever Tick. — This is accomplished in one of 
two general ways or by a combination of the two ; namely, first by the 
application of tickicides on cattle, and secondly by pasture rotation 
resulting in the starvation of the seed ticks which have hatched from 
the eggs deposited by dropped ticks, the pasture being previously made 
free of ticks by a similar process. It is not the object of this work to 
give a detailed account of the methods employed, hence the reader is 
referred to Farmers' Bulletin 498, U. S. Department of Agriculture, for 
specific " Methods of exterminating the Texas fever tick." 

First, agents for the destruction of ticks on cattle are ordinarily 
either oil or arsenic. If the former is used an emulsion is desirable, to 
be applied with a spray pump or in the form of a dip. An emulsion of 
crude petroleum recommended by the U. S. Department of Agriculture, 
Bureau of Animal Industry, 1 is prepared as follows : 

Hard soap 1 pound 

Soft water 1 gal. 

Beaumont crude petroleum 4 gal. 

This formula is sufficient to make five gallons of 80 per cent stock 
emulsion. For use this must be diluted with water to a 20 to 25 per 
cent emulsion, or one part stock emulsion to three or two and one-fifth 
parts of water. 

To prepare the stock the soap should be " shaved up and placed in 
a kettle or caldron containing the required amount of water. The water 
should be brought to a boil and stirred until the soap is entirely dis- 
solved. Enough water should be added to make up for the loss by 
evaporation during this process. The soap solution and the required 
amount of oil are then placed in a barrel or some other convenient re- 

1 Graybill, H. W., 1912. Methods of exterminating the Texas fever tick. 
U. S. Dept. of Agr., Farmer's Bull. 498. 



THE TICKS 309 

ceptacle and mixed. The mixing may be effected by the use of a spray 
pump, pumping the mixture through and through the pump until the 
emulsion is formed. Only rain or soft water should be used for diluting." 
If hard water is used, it should be softened by adding sodium carbonate 
(sal soda), J pound to every five gallons of water used. The Beaumont 
oil recommended has a " specific gravity ranging from 22 J° to 24 J° 
Beaume, containing If to 1| per cent sulphur, and 40 per cent of the 
bulk of which boils between 200° and 300° C." 

Arsenical dips are now more widely used than any other kind. The 
U. S. Department of Agriculture, Bureau of Animal Industry (Graybill, 
1912, loc. cit.), recommends the following formula: 

Sodium carbonate (sal soda) 24 pounds 

Arsenic trioxid (white arsenic) S pounds 

Pine tar 1 gal. 

Water sufficient to make 500 gallons. 

The following directions are given by the Bureau of Animal Indus- 
try for the preparation and use of the above arsenical dip : 

"In preparing the dip a large caldron or galvanized tank is required for 
heating the water in which to dissolve the chemicals. Twenty-five gallons of 
water should be placed in the caldron or tank and brought to a boil. The 
amount of sodium carbonate indicated in the formula is then added and dis- 
solved by stirring. When this is accomplished, the required amount of arsenic 
is added and dissolved in a similar manner. The fire is then drawn, and the 
solution permitted to cool to 140° F., or this process may be hastened by the 
addition of cold water. The pine tar is then added slowly in a thin stream 
and thoroughly mixed with the solution by constant stirring. This solution 
should be diluted at once to 500 gallons. 

"The caldron or tank and utensils used in preparing the dip should be kept 
free from grease or oil, as small quantities of these may envelop particles of 
arsenic and prevent or hinder the solution of the arsenic. It should also be 
borne in mind that when hard water is used in the preparation of the dip the 
dissolving of the sodium carbonate (sal soda) in the boiling water results in the 
formation of a fine white or gray insoluble powder or precipitate of lime salts 
which may be taken for undissolved arsenic, and thus lead to the belief that all 
of the arsenic has not gone into solution. 

"The arsenical solution when prepared according to the above method should 
be diluted as soon as the pine tar has been added, in order that the tar may be- 
come properly emulsified. In the concentrated solution the tar tends to separate 
out, especially when the solution becomes cold, and collect in a layer at the 
bottom of the container. Even when the plan of immediately diluting the solu- 
tion is followed a satisfactory emulsion is not always obtained, and some of the 
tar may separate and go to the bottom of the vat. 

"If, however, the acids present in the tar are neutralized by the use of con- 
centrated lye, a good emulsion of the tar in the diluted dip may be obtained. 1 
The neutralization is effected by dissolving 1 pound of concentrated lye in a 
quart of water for every gallon of tar to be used and adding this solution to the 
tar, stirring thoroughly. When the acids of the tar have been properly neutral- 
ized the resulting mixture should be a bright, thick fluid of a dark brown color. 

1 This method of emulsifying the tar has been suggested by the Biochemic 
Division of the Bureau of Animal Industry. 



310 MEDICAL AND VETERINARY ENTOMOLOGY 

Whether the acids have been neutralized or not may be determined by taking a 
small quantity of the tar on the blade of a pocket knife or on a sliver of wood 
and stirring it in a glass of water. If the acids have been neutralized, the tar 
will mix uniformly with the water ; whereas, if they have not been neutralized, 
the tar will float about in the water in the form of various-sized globules that 
will settle to the bottom when the agitation of the water ceases. For all ordinary 
grades of tar one pound of lye to the gallon will be ample to effect neutralization, 
but if on testing it is found that this amount has not been sufficient, it will be 
necessary to add more lye solution, about a pint at a time for each gallon, until 
the test shows that the acids have been neutralized. The neutralized tar should 
be added to the diluted arsenical dip and not to the concentrated solution, with 
which it will not mix satisfactorily. When the neutralized tar is used the vat 
should be filled with diluted arsenic-soda solution prepared in the usual way. 
The required amount of neutralized tar, diluted with two to three times its 
volume of water, should then be added to the solution in the vat and thoroughly 
mixed with the same by stirring. 

" Before filling a vat the capacity, at the depth to which it is necessary to 
fill it for dipping, if not known, should be calculated, and for future convenience 
the water line should be plainly marked at some point on the wall of the vat. 
Unless this is done it will be necessary either to calculate the amount of water 
in the vat each time it is filled or measure it as it is placed in the vat, both of 
which procedures will consume considerable unnecessary time. The most con- 
venient way to get the water into the vat is to conduct it through pipes, either 
directly from a pump or from an elevated tank used for storing water for farm 
purposes. Frequently, however, it is not possible to bring the water to the vat 
through pipes, and it becomes necessary to resort to the laborious process of 
hauling it in barrels on wagons or sleds. 

"In case the pine tar is added to the concentrated solution when it is made, 
in which case, as already stated, it is necessary to dilute the solution at once, 
the vat should be partly filled with water and then the arsenical solution added 
as it is made. For example, if the vat holds 2000 gallons, about 1500 gallons 
of water should be placed in the vat, then four times the amount of solution for 
making 500 gallons of dip should be prepared and mixed with the water, after 
which the vat should be filled to the 2000-gallon mark. Within certain limits 
it is immaterial just how much water is added at first, provided, of course, ample 
allowance is made for the volume of the concentrated dip so that when it is 
added the dip line will not come above the mark to which the vat is to be filled. 

"The capacity of the vat at a depth of 5 feet 3 inches is 1470 gallons. In 
order to fill it to that depth with dip it will be necessary to prepare two 
batches of concentrated dip, each containing the ingredients necessary for mak- 
ing 500 gallons of diluted dip, and a third batch containing 7 pounds, 9 ounces 
of arsenic and 22 pounds, 3 ounces of sodium carbonate in case 8 pounds of 
arsenic are being used to the 500 gallons, or 9 pounds, 7 ounces of arsenic and 
22 pounds, 8 ounces of sodium carbonate in case 10 pounds of arsenic are being 
used to the 500 gallons. 

"The arsenical dip may be left in the vat and used repeatedly, replenishing 
it with the proper quantities of water and stock solution when necessary. When, 
however, the dip becomes filthy through the addition of manure and dirt carried 
in by the cattle, the vat should be emptied, cleaned, and filled with fresh fluid. 
The frequency with which this should be done must be left to the owner, as the 
condition of the dip at any period after it has been made depends on a variety 
of conditions, such as the number of cattle dipped, and the frequencjr of the 
dippings, etc. Even though the dip may not become very filthy, its efficiency 
decreases somewhat on standing, owing to gradual oxidation of the arsenic. It 
is therefore advisable to recharge the vat at intervals irrespective of the con- 
dition of the dip to cleanliness." 



THE TICKS 311 

Precautions. — From the time the arsenic is purchased to the final 
disposal of the old dip, great care should be exercised in storing, handling 
and using the same owing to the very poisonous nature of the chemical. 
" Cattle should always be watered a short time before they are dipped. 
After they emerge from the vat they should be kept on a draining floor un- 
til the dip ceases to run from their bodies ; then they should be placed in 
a yard free of vegetation until they are entirely dry. If cattle are al- 
lowed to drain in places where pools of dip collect from which they may 
drink, or are turned at once on the pasture, where the dip will run from 
their bodies on the grass and other vegetation, serious losses are liable to 
result. Crowding the animals before they are dry should also be avoided, 
and they should not be driven any considerable distance within a week 
after dipping, especially in hot weather. If many repeated treatments 
are given, the cattle should not be treated oftener than every two weeks. 

" In addition to properly protecting vats containing arsenical dip 
when not in use another precaution must be observed when vats are 
to be emptied for cleaning. The dip should not be poured or allowed to 
flow on land and vegetation to which cattle or other animals have access. 
The best plan is to run the dip into a pit properly protected by fences. 
The dip should also not be deposited where it may be carried by seepage 
into wells or springs which supply water used on the farm." 

Procedure. — After having exercised the precaution of watering 
them, the cattle to be dipped are driven from a pen one by one into 
the chute and thence into the dip (Fig. 192). The plunge is likely to 
wet the animal all over, but a second plunge of the head into the dip 
near the middle of the vat by means of a forked stick is advised so that 
the head is really plunged under twice in passage through the dip. 
After drying, the cattle should be driven on to a tick-free pasture and 
the process repeated in from seven to ten days in order to destroy all 
ticks which may have escaped the action of the first dipping. 

Pasture Rotation. — Exterminating ticks by pasture rotation is 
based on the time required to kill the ticks by starvation. Inasmuch 
as the longevity of ticks depends on moisture and temperature mainly, 
local conditions affecting the same must be taken into consideration. 
Cold and moisture prolong life, while dryness and heat shorten the same. 

In pasture rotation the cattle are kept off of a given pasture for a 
given length of time, after which they are moved to a third area, etc., 
until all ticks have matured and have dropped from the cattle and 
have died from starvation on the earlier plots. Thus a field should be 
divided into three or more plots each separated by means of two fences 
about fifteen feet apart to reduce the opportunity of ticks to crawl 
from one plot to the other. 

Various plans requiring from four and a half to eight months have 
been devised to free both cattle and pasture from ticks. Thus a plan 
requiring four and one half months is described by Graybill (1912, loc. 
cit.) (Fig. 193). He advises dividing the pasture in the middle by two 



312 MEDICAL AND VETERINARY ENTOMOLOGY 




o 



ti 



THE TICKS 



313 



FIELD N02B. 
OCT. 12 MOVE THE HERD . 
TO FIEID A/O.J. 



OATS FOLWmi BY 



1THER 



CQWPEASOR 
FDR ABE 



FIELDN0.2A. 
SEFTZZMOVEJHB 
HERD TO FIELD 
NO.Z B. 



FIELD NO.*. 
COTTON. 
RYE OR CRIMSON 
GLOVER. 



lines of temporary fence fifteen feet apart. This to be done some time 
in the spring. The herd is first kept in field No. 1A, and is then re- 
moved, on June 15, to field No. IB, and on September 1 to field No. 
2 A. The cattle must remain twenty days on fields 2 A, 2B, and 3. 
At the end of this time, which would be November 1, all the ticks will 
have dropped and the herd is returned to field No. 1A, which has be- 
come free from ticks in the meantime. Field No. IB becomes free 
from ticks July 1 of 
the following year, 
when the double fence 
between 1A and IB 
may be removed and 
the cattle may then 
(and not before) graze 
over both fields. By 
August 1 the entire 
farm will be free from 
ticks. 

Graybill advises 
as above that double 
fences be built be- 
tween all the fields, 
when practicable, in 
order to prevent ticks 
from getting from 
one field to another. 
In place of the extra 
line of fence the next 
best thing would be 
to " throw up several 
furrows with a plow 
on each side of the 
dividing fences." If 

Streams run through Fig. 193. — Plan for freeing cattle and pastures from ticks 
,i » ,i by rotation, requiring four and one half months. (Re- 

the larm or the drawn after Graybill.) 

slope of the land is 

considerable, so that ticks may be washed from field to field, he ad- 
vises arranging the fields so that drainage is from field No. 1A to No. 
IB, and from No. 3 toward fields Nos. 2A and 2B. 

African coast fever, also known as Rhodesian red water, occurs 
along the east coast of Africa, including Rhodesia and the Transvaal. 
The mortality is said to range close to 90 per cent. The causative 
organism is Theileria parva (Theiler). The symptoms of the dis- 
ease, according to Robertson, 1 are described as follows : " These are 



FIFLD MS 
CORN. 
COWPFAS. 



NOV! MOVETHE HERD TO 
FIELD mi A. 



mrnn 

HOUSE- 

mm 



PASTURE: BERMW VEtCH\ AMD BURR CLOVER. 



FIELO NO.IB. 



HELD I 
WILL BE FREE OF TICKS AND 7NE i 

Temporary double fenced ysE\ 

REMOI/FD. i 



I 

FIELD /HO /A- 
K JUAIEI5.MoyE THE HERD TO FIELD 
\*0IB. KEEP BUT ALL AN I M Ms 
\FRQM THIS DATE UNTIL AIM. WHEN 
(THIS FIELD WILL BB FPSE OF TICKS. 
I 
I 



1 Robertson, W. 
of Agr. Bull. 18. 



1904. African coast fever. Cape of Good Hope, Dept. 



314 MEDICAL AND VETERINARY ENTOMOLOGY 

neither very definite nor characteristic. The disease runs its course in 
from twelve to fifteen days, dating from the time the animal is first 
noticed sick. The temperature is high, 106° to 107° F. There is run- 
ning from the eyes and nose, and symptoms of pain in the abdomen. 
Purging and diarrhea are frequently seen. In the later stages the dung 
may contain blood and be dark in color. The animal's brain usually 
becomes affected before death, which is preceded by stupor and coma. 
If the lungs become involved there is great distress in breathing, ac- 
companied by a short cough." Lounsbury's x experiments demon- 
strate that African coast fever may be transmitted to susceptible 
cattle from actually sick ones through the medium of five species of 
ticks of the genus Rhipicephalus, namely jR. appendiculatus, R. evertsi, 
R. simus, R. capensis, and R. nitens. He succeeded in transmitting the 
disease from twelve sick animals to thirty-five healthy ones by means 
of ticks. The infection was taken by ticks in one stage of the life history 
and transmitted in the next following stage. A dozen or more ticks 
were usually applied in each case ; however he succeeded in infecting 
an animal with one tick alone and in another case by two ticks. The 
ticks are believed to be in constant readiness to transmit infection. 
The incubation period was found to average thirteen and one-half 
days and ranged from nine to nineteen days. While the duration of 
the cases averaged twelve days, it was found that few of the animals 
appeared seriously ill until a few days before death, an important factor 
in the dissemination of the disease in the veldt during the time that the 
infective animal is active. 

Other important discoveries were that the disease did not result 
from ticks fed on recovered animals, neither from the progeny of ticks 
from sick animals, nor from adults which as nymphs had fed on im- 
mune animals, but as larvae had fed on sick animals. 

Spotted Fever. — Spotted fever has been known in the Bitter Root 
Valley of Montana (U. S. A.) since 1872, 2 also known as "tick fever," 
" black fever," "blue disease," "black measles," and " piroplasmosis 
hominis." The causative organism is doubtfully referred to as Piro- 
plasma hominis (Wilson and Chowning). The most characteristic and 
constant symptom is the eruption which appears about the second to 
the fifth day on the wrists, ankles and back, later spreading to all parts 
of the body and lasting from a few days (8 to 21) to several months : 
" These spots are petechial and not raised ; at first they are rose-colored 
and disappear momentarily upon pressure ; but later they become per- 
manent and assume a dark blue or purplish color; they may coalesce 
and give a mottled or marbled appearance to the skin; they may or 

1 Lounsbury, Chas. P., 1906. Ticks and African coast fever. Agric. 
Journ. of the Cape of Good Hope, Vol. XXVIII, No. 5, pp. 634-654. 

2 Stiles, Ch. Wardell, 1905. A zoological investigation into the cause, 
transmission and source of Rocky Mountain "spotted fever." Treasury 
Dept. Public Health and Marine Hospital Service of the United States. Hygiene 
Lab. Bull. No. 20, pp. 121. 



THE TICKS 315 

may not be tender to the touch. . . . The fever develops rapidly, 
and may register 102° to 104° or 105° F., when the patient takes to 
bed. It gradually reaches its maximum in two to seven days, when it 
ordinarily registers 103° to 106°. 

" Both sexes and all ages are subject to the disease, but it is more 
common in males from 21 to 40, and in females from 11 to 40 years of 
age, than at other times of life. ... A lethality of 70.5 per cent was 
shown for 139 collated cases ... 100 per cent for all patients over 60 
years old. So far as one could judge occupation seems to play a role, 
for a very large percentage of the patients are on farms or are connected 
with the lumbering industry" (Stiles, 1905, he. cit.). 

In Idaho a mild type of the disease exists, with a mortality of about 
1 to 3 per cent according to Stiles and from 5 to 7 per cent according 
to Hunter and Bishopp. 

Tick Transmission of Spotted Fever. — After a preliminary inves- 
tigation Wilson and Chowning l in 1902 advanced for the first time the 
theory that a tick ("wood tick") acts as the natural vector of the dis- 
ease. According to Rickette (in 48th Biennial Rept. Montana State 
Board of Health, p. 106) as recorded by Hunter and Bishopp 2 " the 
first experiments which resulted in the proof of the transmission of 
spotted fever by a tick were conducted by Doctors McCalla and Brere- 
ton of Boise, Idaho, in 1905. In these experiments a tick which was 
found attached to a spotted fever patient was removed and allowed to 
bite a healthy person. In eight days this person developed a typical 
case of spotted fever. The experiment was continued by allowing the 
same tick to bite a second person. In this case again a typical case of 
spotted fever resulted." 

The famous experiments of Doctor H. T. Ricketts began in April, 
1906. The more important published work of this lamented investi- 
gator has been brought together in a memorial volume 3 from which 
the following summary is made of his reports on spotted fever. First 
of all it was shown that the disease could be transmitted to guinea pigs 
by direct inoculation and that the duration of the fever and cutaneous 
phenomena resembled very closely the conditions as observed in humans. 
Hence, knowing the susceptibility of this species, it was used for further 
experimentation. 

On June 19, 1906, a small female tick was placed at the base of the 
ear of a guinea pig inoculated intraperitoneally June 11 with 3 cc. of 
defibrinated blood of a spotted fever patient. The tick fed for two 

1 Wilson, Louis B., and Chowning, William M., 1902. The so-called 
"spotted fever" of the Rocky Mountains. A preliminary report to the Mon- 
tana State Board of Health. Journ. Amer. Med. Assoc, Vol. 39, No. 3, pp. 
131-136. 

2 Hunter, W. D., and Bishopp, F. C, 1911. The Rocky Mountain spotted 
fever tick. U. S. Dept. of Agric, Bur. of Ento. Bull. 105, pp. 47. 

3 Ricketts, H. T., 1911. Contributions to Medical Science. The Univer- 
sity of Chicago Press. 497 pp. (See pp. 278-450.) 




316 MEDICAL AND VETERINARY ENTOMOLOGY 



days on this animal and was then removed and kept for two days in a 
pill box and on June 23 placed at the base of the ear of a healthy 
guinea pig, the former animal dying on the same day with characteristic 
symptoms. On June 28 the second guinea pig showed a decided rise 
in temperature, which continued high until July 5 and became normal 
on July 7. Proper controls were conducted and two guinea pigs which 
were in the same cage with the tick-bitten guinea pig for two weeks 
did not become infected, indicating that mere association did not 
result in contracting the disease. 

In addition to many other successful experiments during the follow- 
ing year Ricketts found that the disease can be transmitted by the 
male as well as by the female tick and that " one attack of the disease 
establishes a rather high degree of immunity to subsequent inocula- 
tion." Furthermore a collection of ticks taken in the field transmitted 

the disease to a guinea pig 
in the laboratory, indicat- 
ing the fact that infective 
ticks occur in nature in 
probably small numbers. 

It was also ascertained 
that " the disease may be 
acquired and transmitted 
... by the tick during 
any of the active stages 
. . . and that the larvse of 
an infected female are in 
some instances infective. 
. . . The disease proba- 
bly is transferred through 
the salivary secretion of 
the tick, since the salivary 
glands of the infected adult contain the virus." The transmission is 
believed to be " biological rather than purely mechanical." 

Experiments conducted by Moore (Ricketts, 1911, loc. cit., pp. 428- 
436) show that the " minimum duration of feeding necessary for a tick 
to infest a guinea pig was one hour and forty-five minutes. The aver- 
age time necessary seems to be about ten hours, while twenty hours 
were almost constantly infective." Maver (see Ricketts, 1911, loc. cit., 
pp. 440-444) in a series with other species of ticks found that spotted 
fever can be transmitted from infected to normal guinea pigs by Der- 
macentor variabilis, Dermacentor marginatus and Amblyomma ameri- 
canum, in addition to Dermacentor venustus. 

Ricketts' careful observations with regard to the causative organ- 
ism failed to substantiate the findings of Wilson and Chowning that the 
disease is of piroplasmic origin, although he failed to secure infective 
virus by passing serum diluted tenfold in physiologic salt solution 




Fig. 194. — The spotted fever tick, Dermacentor 
venustus; male (left), unengorged female (right). 
X 3.5. 




THE TICKS 317 

through a Berkefeld filter. This he states " suggests that the organism, 
though undoubtedly minute, is of such size that it should be recognized 
by the use of high magnifications, or that it is of peculiar form or possesses 
such adhesive properties that it is not readily filterable." 

Rocky Mountain Spotted Fever Tick. — The spotted fever tick, 
Dermacentor wnustus Banks (Fig. 194), possesses the general characters 
of the genus Dermacentor, viz., " Usually ornate, with eyes and festoons ; 
with short, broad or moderate palps and basis capituli rectangular 
dorsally. In some species coxse I to IV of the male increase progres- 
sively in size; in all species coxa IV is much the largest; the male, 
moreover, shows no ventral plates or shields. Coxa I bifid in both 
sexes. Spiracles sub-oval or comma-shaped " (Nuttall, 1911, loc. cit.). 

The species is described by Banks, 1 viz. : 

"Male — red brown, marked with white, but not so extensively as in D. oc- 
cidentalis, usually but little white on the middle posterior region; legs paler 
red-brown, tips of joints whitish. Capitulum quite broad, its posterior angles 
only slightly produced; palpi very short and broad, not as long as width of 
capitulum. Dorsum about one and two-thirds or one and three-fourths times 
as long as broad, with many, not very large, punctures ; lateral furrows distinct. 
Legs of moderate size, hind pair plainly larger and heavier, and with the teeth 
below distinct. Coxae armed as usual, the coxa IV nearly twice as wide at base 
as long. Stigmal plate with a rather narrow dorsal prolongation, with large 
granules on the main part and minute ones on the prolongation. 

" Length of male, 3.5 to 5 mm. 

" Female — Capitulum and legs reddish brown, the latter with tips of joints 
whitish; shield mostly covered with white, abdomen red-brown. Capitulum 
rather broad, posterior angles but little produced, the porose areas rather large, 
egg-shaped, and quite close together; palpi shorter than width of capitulum. 
Shield as broad as long, broadest slight] y before the middle, and rather pointed 
behind, with numerous, not very large punctures. Legs of moderate size, the 
coxae armed as usual. The stigmal plate has a rather narrow dorsal prolonga- 
tion, with large granules on the main part, and small ones on the prolongation. 

"Length of female shield, 2 mm." 

Life History and Habits of Spotted Fever Tick. — The most com- 
plete and satisfactory study of the habits and life history of this species 
has been made by Hunter and Bishopp (loc. cit.), from whose work the 
following account is taken. The winter is passed by the ticks as un- 
engorged males, females and nymphs. They begin attacking their 
warm-blooded hosts, including man, about March 15 and continue so 
doing to about July 15. During this period the female deposits eggs. 
The overwintering nymphs transform to adults during the summer and 
autumn and pass the winter in an unengdrged condition, thus requiring 
about two years for their development. As much as three years may 
be required for complete development under unfavorable conditions. 

The engorged females after being fertilized drop from the host 

1 Banks, Nathan, 1908. A Revision of the Ixodoidea, or Ticks, of the 
United States. U. S. Dept. of Agr. Bur. of Ento. Technical Series, No. 15, 
61 pp. 



318 MEDICAL AND VETERINARY ENTOMOLOGY 

animal and deposit about 4000 eggs within thirty days, beginning to 
deposit as early as the seventh day after dropping. The eggs are ovoid, 
brownish in color and about one thirty-eighth of an inch long. The in- 
cubation period ranges from thirty-four to fifty-one days in the Bitter 
Root Valley (15-41 days at Dallas, Texas) . The newly emerged hexapod 
seed ticks shortly after hatching crawl up blades of grass or other objects 
and await the coming of a host, usually one of the smaller species of 
rodents, e.g. ground squirrels, chipmunks, woodchucks, pine squirrels 
and wood rats. 

After attaching to the host the larvae become filled with blood in 
from three to eight days, after which they drop off and molt in from six 
to twenty-one days, emerging from this stage with eight legs, — a 
nymph. Nymphs emerging from the larval or seed tick stage late in 
summer or autumn pass the winter as nymphs, others find a second host, 
either a small mammal or less commonly a larger wild or domesticated 
animal. The feeding period requires from four to nine days, when the 
engorged nymphs drop to the ground and in twelve to sixteen days and 
over, molt for the second time, emerging as adults. 

The adults now by preference attach themselves to larger domesti- 
cated animals. After feeding about four days the males search their 
mates, mating on the host animal, and after eight to fourteen days after 
attachment the engorged females drop to the ground and deposit their 
eggs in some protected place near by. The life cycle requires two years 
in the majority of cases ; however, in some one season is sufficient. 

The fully engorged females are " about one half inch long by one 
third inch wide by one fourth inch thick. On account of the enormous 
distention of the back part of the body of the female, the legs and head 
are rendered inconspicuous. A close examination^ however, will show 
the white shield on the back just behind the ' head.' " The males are 
about the same size as the females before engorgement, and have the 
shield (scutum) covering the entire back, whereas in the female the 
shield is much smaller (Fig. 194). 

Longevity. — Hunter and Bishopp (1911, he. cit.) have " found 
that all unfed seed ticks hatching from a mass of eggs usually die within 
one month after the first eggs hatch. In one instance a period of 117 
days elapsed between the beginning of hatching of the eggs and the 
death of the last seed tick. (A later record by these workers exceeded 
317 days.) Unfed nymphs have been found to survive a period of one 
year and eleven days, and adults collected on vegetation during the 
spring months may survive for a period of 413 days without food." 

Distribution. — Bishopp x states that the northern part of the 
Rocky Mountain region of the United States is the territory prin- 
cipally infested, but the river valleys and sagebrush plains in the west 
are more or less heavily infested, — Idaho, Wyoming, Montana, parts 

1 Bishopp, F. C, 1911. The Distribution of the Rocky Mountain Spotted- 
fever Tick. U. S. Dept. of Agr., Bur. of Ento. Circ. No. 136. 



THE TICKS 319 

of Utah, Colorado, Nevada, Oregon, Washington, California and 
southern British Columbia being involved. The species is believed to 
occur in greatest numbers between 3000 and 5000 feet. 

Control of Spotted Fever Tick. — Knowing that the most important 
agent, if not the sole agent under natural conditions, in the dissemina- 
tion of spotted fever is Dermacentor venustus, it becomes evident at 
once that the control of this tick is essential to the control of the disease. 

Since the principal hosts for the adult stage of the tick are the 
larger domesticated animals, principally horses and cows, these animals 
must be kept free from ticks by the application of ordinary tick control 
measures (see under Texas fever). Because the tick requires at least 
two years to complete its life history, domesticated animals must be 
kept free from ticks for at least two consecutive years. In this way 
maturity is prevented and no eggs will be deposited to furnish a new 
supply of seed ticks to feed on smaller rodents. No doubt also much 
exterminative work must be done against the smaller rodents, as well 
as the larger wild animals. 

The most significant step toward the control of spotted fever in 
Montana was taken by the legislature of that state in 1913, when a 
bill was passed creating a State Board of Entomology, with authority 
to act, and appropriating $5000 per annum for its use during a period of 
two years. The act seems so significant that it is here given in full : 

"An Act to Create the State Board of Entomology. To define its powers 
and duties and appropriate money therefor. 

"Be it enacted by the Legislative Assembly of the State of Montana. 

"Section 1. There is hereby created the Montana State Board of En- 
tomology, which shall be composed of the State Entomologist, the Secretary 
of the State Board of Health and the State Veterinarian. 

"Section 2. The Secretary of the State Board of Health shall be Chairman 
of said Board and the State Entomologist shall be Secretary. 

"Section 3. None of the members of said Board shall receive any com- 
pensation other than that already allowed by law, except that the actual expense 
of members while engaged in the duties incident to the work of said board shall 
be paid out of the appropriation made to carry on the w r ork of said board. 

"Section 4. It shall be the duty of said board to investigate and study the 
dissemination by insects of diseases among persons and animals, said investi- 
gation having for its purpose the eradication and prevention of such dis- 
eases. 

"Section 5. Said board shall take steps to eradicate and prevent the spread 
of Rocky Mountain tick fever, infantile paralysis and all other infections or 
communicable diseases that may be transmitted or carried by insects. 

"Section 6. Said board shall have authority to make and prescribe rules and 
regulations including the right of quarantine over persons and animals in any 
district of infection and shall have the right, to designate and prescribe the 
treatment for domestic animals to prevent the spread of such diseases ; but said 
board shall not have the right to prescribe or regulate the treatment given to 
any person suffering from any infectious or communicable disease. 

"Section 7. All rules and regulations of the State Board of Entomology shall 
be subject to approval by the State Board of Health. 

"Section 8. The board shall publish in printed form all rules and regulations 



320 MEDICAL AND VETERINARY ENTOMOLOGY 

which shall be adopted by said board for the eradication and control of diseases 
of any kind and such rules and regulations shall be circulated among the resi- 
dents of every district affected thereby. 

"Section 9. Any person who shall violate any of the rules or regulations of 
the State Board of Entomology shall be deemed guilty of a misdemeanor and 
upon conviction thereof shall be fined in any sum not in excess of one hundred 
($100.00) dollars, or by imprisonment in the County Jail for any period not 
exceeding thirty (30) days Or by both such fine and imprisonment. 

"Section 10. There is hereby appropriated out of any moneys in the State 
Treasury not otherwise appropriated the sum of five thousand ($5000.00) 
dollars, or so much thereof as may be necessary to carry on the work of the 
State Board of Entomology for the year 1913, and the sum of five thousand 
($5000.00) dollars or so much thereof as may be necessary to carry on the work 
of said board for the year 1914. Said money to be expended under the direc- 
tion and approval of the State Board of Examiners. 

"Section 11. All Acts or parts of Acts in conflict with this Act are hereby 
repealed. 

"Section 12. This Act shall take effect from and after its passage and 
approval. 

"Approved March 18, 1913." 

Other Piroplasmoses. — At least two types of piroplasmoses are 
found in horses and mules, namely true equine piroplasmosis, trace- 
able to Babesia caballi (Nuttall), occurring in Russia, Transcaucasia 
and probably Siberia, and secondly a similar though distinct disease 
traceable to Nuttallia equi (Laveran) occurring in Transcaucasia, Italy, 
Africa, India and South America (Brazil). The former is transmitted 
by Dermacentor reticulatus while the latter is transmitted by Rhipiceph- 
alus evertsi. 

Ovine piroplasmosis traceable to Babesia ovis (Babes) occurs 
in sheep in Transcaucasia, Roumania, Turkey and probably also in 
northern Africa. The disease is carried by the tick, Rhipicephalus 
bursa. k 

Canine piroplasmosis, also known as " malignant jaundice " of dogs, 
is prevalent in Europe, Asia and Africa. The causative organism is 
Babesia canis Piana and Galli-Valerio and the carrier is Rhipicephalus 
sanguineus in India, Europe and North Africa ; Hamaphysalis leachi 
is the carrier in other parts of Africa. 

Tick Paralysis. — A very striking form of paralysis induced by the 
bite of Dermacentor venustus has been reported * as occurring in both 
sheep and man (children), also in other animals (dog and rabbit), in 
British Columbia and Montana. In lambs the paralysis develops 
gradually, beginning with a staggering gait, bumping against obstacles 
and occasionally falling, finally failing to rise. The attack is usually 
of short duration but may persist for long periods and may terminate 
fatally. The symptoms appear in from six to seven days after the ticks 
have become attached. It is believed that the disease is caused by the 

1 Hadwen, Seymour, 1913. On "Tick paralysis" in sheep and man fol- 
lowing bites of Dermacentor venustus. Parasitology, Vol. VI, No. 3, pp. 293- 
297, with 2 plates. 



THE TICKS 



321 




Fig. 195. — A common deer and cattle 
tick of California, Ixodes ricinus var. 
calif ornicus ; female (left), male (right). 
X 3.5. 



inoculation of a toxin from the tick. It has also been observed that the 
ticks attach themselves by preference along the spinal column of the 
host, and at the nape of the neck in man. 

Other Ixodine Ticks. — Over forty species of ticks (mostly Ixo- 
dine) are known to occur in the United States alone, and many 
other species occur in the tropics. 
For the disease-bearing and ven- 
omous species it may be said 
that a single individual may be of 
great importance, while the eco- 
nomic importance of the innocuous 
species depends on relative abun- 
dance. The most widely distrib- 
uted and abundant genera are 
Ixodes and Dermacentor. Ixodes 
ricinus Linn., commonly called the 
" castor bean tick," is found in 
Europe, America, Asia and Africa, 
and attacks many species of warm- 
blooded animals. Ixodes ricinus 
var. calif ornicus Banks (Fig. 195) 

is commonly found in California on the black-tailed deer, the bobcat 
and other species of wild animals, also frequently and abundantly on 
cattle. The common " dog tick " or "wood tick" also attacks many 
species of warm-blooded animals, among them horses, cattle, dogs and 
man. When abundant these species are of considerable importance. 
In the eastern part of the United States Dermacentor variabilis Say 

. is the most common, while along the Pacific 

Coast it is largely replaced by Dermacentor occi- 

Jjj^£^- dentalis Neumann (Fig. 196). In the southern 

ft - part of the United States, particularly Texas and 

JM wt\ Louisiana, the " lone star tick," Amblyomma 

/ | americanum Linn. (Fig. 197) is very common. 

V Hr The " rabbit tick," Hwmayhysalis leporis = 

^^^ palustris Packard, is a widely distributed and 

abundant species on rabbits, while Rhipicephalus 

196. Western dog sanguineus Latreille is known as the "brown 

dog tick " and is almost a cosmopolitan species. 
Nuttall (1911, loc. cit.) includes nine genera 
in the family Ixodidse, namely : — Ixodes, Hsemaphysalis, Dermacentor, 
Rhipicentor, Rhipicephalus, Margaropus, Boophilus, Hyalomma 
and Amblyomma (Aponomma). "Ixodes is clearly marked off from 
the other genera by a number of characteristics, of which the most 
striking are the anal groove surrounding the anus in front (Prostriata) 
and the absence of festoons. The remaining genera fall naturally 
into two divisions : the one characterized by a comparatively short, 



Fig. 

or wood tick, Dermacen- 
tor occidentalis. X 2.5. 



322 MEDICAL AND VETERINARY ENTOMOLOGY 






and the other by a comparatively long, capitulum." Nut tall further 
arranges these as follows : 

Ixodidae 



Prostriata 



"I 

Metastriata 



i 
Brevirostrata 



Longirostrata 



Group 1 
1 Ixodes 2 Hsemaphysalis 



Group 1 



Group 2 

I 

S Hyalomma 9 Amblyomma 



Group 2 

I 

3 Dermacentor 

4 Rhipicentor 

5 Rhipicephalus 

6 Margaropus 

7 Boophilus 

" Ixodes : inornate; without eyes and without festoons; spiracles 
round or oval ; palpi and basis capituli of variable form ; coxse either 
unarmed, trenchant, spurred or bifid ; tarsi without spurs. Sexual 
dimorphism pronounced, especially with regard to the capitulum; in 
the male the venter is covered by non-salient plates ; one pregenital, one 
median, one anal, two adanal and two epimeral plates." 

" Haemaphysalis : inornate, without eyes but with festoons ; with 

usually short conical palpi whose 
second articles project laterally 
beyond the basis capituli, which 
is rectangular dorsally. With 
dorsal process on first trochanter. 
Usually of small size and but 
slightly chitinized. Sexual di- 
morphism slight. The male shows 
no ventral plates or shields. 
Spiracles in male usually ovoid 
or comma-shaped ; in female 
rounded or ovoid." 

" Dermacentor: usually 
ornate, with eyes and festoons; 
with short, broad or moderate palpi and basis capituli rectangular 
dorsally. In some species coxae I to IV of the male increase progres- 
sively in size ; in all species coxa IV is much the largest ; the male, 
moreover, shows no ventral plates or shields. Coxa I bifid in both 
sexes. Spiracles suboval or comma shaped." 

''Rhipicentor: inornate, with eyes and festoons; with short 
palpi, with basis capituli hexagonal dorsally and having very prominent 
lateral angles. Coxa I bifid in both sexes. The male resembles 
Rhipicephalus dorsally, Dermacentor ventrally : coxa IY is much the 




Fig. 197 



- The lone star tick, Amblyomma 
americanum. X 3.5. 



THE TICKS 323 

largest; no ventral plates or shields; spiracles subtriangular (female) 
or comma-shaped (male)." 

" Rhipicephalus : usually inornate, with eyes and festoons; 
with short palpi and basis capituli usually hexagonal dorsally. . . . 
Coxa I bihd. The male possesses a pair of adanal shields and usually 
a pair of accessory adanal; some males, when replete, show a caudal 
protrusion. Spiracles bluntly or elongate comma-shaped." 

" Margaropus : l inornate, with eyes, but without festoons, with 
short palpi and capitulum intermediate between that of Rhipicephalus 
and Boophilus; highly chitinized, the unfed adults of large size. The 
female with very small scutum. Coxae conical, unarmed but for a 
small spine posteriorly on coxa I. The male with a median plate 
prolonged in two long spines projecting beyond and to either side of 
the anus ; with coxae similar to those of the female ; legs increasing 
progressively in size from pair I to IV, the articles especially of leg-pair 
IV greatly swollen. When replete, the male shows a caudal protrusion. 
Anal groove obsolete. Spiracles rounded or short-oval in both sexes." 

" Boophilus : inornate, with eyes, but without festoons ; with 
very short compressed palpi ridged dorsally and laterally ; basis capituli 
hexagonal dorsally ; slightly chitinized ; the unfed adults of small size. 
Coxa I bifid. Anal groove obsolete in female, faintly indicated in male. 
The female with a small scutum ; the male with adanal and accessory 
adanal shields. Spiracles rounded or oval in both sexes." 

" Hyalomma : ornamentation absent or present, at times con- 
fined to the legs ; with eyes, with or without festoons, with long palpi 
. . . and basis capituli subtriangular dorsally. The female approaching 
Amblyomma. The male with a pair of adanal shields, and with or with- 
out accessory adanal shields and two posterior abdominal protrusions 
capped by chitinized points. Coxa I bifid. Spiracles comma shaped." 

"Amblyomma: generally ornate, with eyes and with festoons. 
With long palpi, of which article 2 is specially long ; basis capituli of 
variable form. The male without adanal shields, but small ventral 
plaques are occasionally present close to the festoons. Spiracles sub- 
triangular or comma-shaped" (Xuttall). 

The Argasixe Ticks 

Agas persicus Oken = A. miniatus Neumann = A. americanus 
Packard, a cosmopolitan fowl tick, is one of the most important poultry 
parasites in existence (Fig. 198). Other than "fowl tick" this pest 
is commonly called " adobe tick " or " tampan." In color it varies 
from a light reddish brown to a dark brown, depending on the stage 
of engorgement. In size the obovate, flattened adults average about 
8.5 mm. long by 5.5 mm. wide in the female, and 6.5 mm. long by 

1 Does not include Margaropus annulatus = Boophilus annulatus. 

Y 



324 



MEDICAL AND VETERINARY ENTOMOLOGY 




Fig. 198. — The poultry tick, Argas (miniatus) 
persicus, ventral and dorsal views. X 3.5. 



4.5 mm. wide in the male. When unengorged their thickness is about 
.75 mm., and when fully engorged may be nearly 3 mm. at the thickest 
part. The edges are always very thin even when engorged. The sexes 

are not easily distinguish- 
able; the males are smaller, 
but may be as large as 
smaller female individuals, 
and taper slightly more an- 
teriorly, i.e. are more obo- 
vate. The genital orifice of 
the male is " half-moon 
shaped," while in the female 
it is "slit-like" and situated 
farther forward, i.e. imme- 
diately behind the capitulum. 
The capitulum has four long 
hairs, two hypostomal, and 
one near the articulation of 
each palp, all directed for- 
wards. The palps are about twice as long as the hypostome, second 
article longest, the others equal in length. The hypostome has 6 or 
7 fine denticles on each half distally, followed by stout teeth |, the 
numbers increasing to |, f , f , basally, the teeth decreasing in size, not 
attaining the external border nor extending beyond half the length 
of the hypostome (Nuttall). 

Life history and habits. — The nymphs and adults of Argas persicus 
are strikingly active at night, migrating long distances to find their 
host, and hiding in an inactive condition during the day. The writer 
has observed this pest in vast 
numbers hiding beneath the 
loose bark of the eucalyptus tree 
in California. Occasionally spe- 
cimens are sent in with the in- 
quiry, " are they parasites of 
the tree or do they attack 
roosting chickens, the chickens 
seem to do very poorly, yet we 
find nothing on them ? " At 
night if one observes some- 
what closely, one may see hordes 
of these ticks climbing up the 
sides of the chicken coop to the roosts and upon the fowls, filling up 
leisurely with blood and before daybreak departing for their hiding 
places. The females deposit their large reddish brown eggs in the 
crevices occupied during the day. The eggs are laid in masses of 
from 25 to 100, more or less, and there are usually several layings, 




Fig. 199. — Larva of the poultry tick, Argas 
(miniatus) persicus. X 30. 






THE TICKS 325 

once after each meal. Egg deposition occurs very readily in al- 
most any sort of receptacle in which the ticks may be kept for 
observation. Hatching takes place in from three to four weeks. The 
larvae (Fig. 199) are six-legged and very active, attacking a host 
apparently as readily by day as by night. Once attached the larvae 
feed for about five days, occasionally longer, remaining firmly attached 
during this time. When fully engorged they appear like little reddish 
globules, causing severe irritation. At the end of this feeding period 
the larvae detach themselves, having become rather flattened in the 
meantime and then crawl away from the host, hiding in some convenient 
crevice near by. The larvae molt in about a week, when the fourth 
pair of legs appears and they are now in the first nymphal stage, appear- 
ing like miniature adults. Nocturnal feeding now takes place and in 
ten or twelve days another molt occurs and the second nymphal stage 
is reached. Again the tick attaches itself, being now able to engorge 
itself in about an hour ; again after the expiration of something over a 
week a third molt takes place and the adult stage is reached. The 
adults are able to engorge themselves in from 20 to 45 minutes. 

Since eggs are deposited mainly during July in California, the adult 
stage may or may not be reached before the rainy season begins, and the 
overwintering stage may be in the second nymphal condition or as 
adults, appearing in pestiferous numbers early during the following 
summer. Hence there is ordinarily one generation of ticks per year 
under normal conditions. In the absence of a host this species mani- 
fests a striking longevity of a year and over (a little over two years 
according to Lounsbury). 

Damage Done. — Each tick when engorging requires considerable 
blood to become replete, hence, when myriads of these parasites attack 
fowls great quantities of blood must be extracted. The writer has 
known of chickens being picked up under the roost in the morning with 
no apparent cause for death, and believes this to have been due directly 
to the work of ticks. Weakened and unthrifty condition of a flock may 
be traceable solely to ticks. Poultry suffering from ticks have dull, 
ragged plumage, suffer from diarrhea, are weak and lay poorly. 

Fowl Spirochetosis. — A very fatal disease, known as " fowl spiro- 
chetosis/' is traceable to Spirochceta marchouxi Nuttall = Spirochceta 
gallinarum Blanchard, occurring in India, Australia, Brazil, Egypt and 
Persia, and is no doubt very widely distributed. The disease attacks 
chickens, geese, turkeys, guinea fowls and other birds. The symptoms 
are described as follows : 

" The disease begins with diarrhea, followed by loss of appetite, 
the birds appearing somnolent ; the feathers being ruffled and the comb 
pale. The birds cease to perch, lie down with the head resting upon 
the ground and death takes place during a convulsive attack. At 
times the disease runs a slower course, the legs become paralyzed, then 
the wings, and the bird grows thin and dies in eight to fifteen days. 



326 MEDICAL AND VETERINARY ENTOMOLOGY 

Recovery may take place, but it is rare after paralytic symptoms have 
appeared. At autopsy, during the acute period of the disease, the 
spleen appears much enlarged and the liver swollen with more or less 
fatty degeneration, at times the liver is dotted with focal necroses. In 
chronic cases both these organs may appear atrophied. The blood is 
fluid and dark. Spirochetes are plentiful in the blood until shortly 
before death, and they disappear as recovery sets in " (Xuttall). 

Argas persicus has been proved to be the carrier by Marchoux and 
Salimbeni, Balfour, Nuttall and others. These investigators have 
found that when this tick sucks blood from an infected fowl 
the spirochetes multiply within the body of the same when kept at 
from 30° to 35° C. and are capable of transmitting the disease; but 
when they are kept at from 15° to 20° C. they fail to transmit it. How- 
ever, if the ticks are later kept in the higher temperature they become 
infective. The spirochetes are transmitted by the bite and the ticks 
are said to be infective for six months or more. The incubation period 
in the fowl is from four to nine days. 

Combating the Fowl Tick. — Henhouse roosts should be painted 
thoroughly with kerosene or gasoline and put in position with the ends 
in cups of crude oil or tar or embedded in oil-soaked waste, or suspended 
by wires from the ceiling. Roost poles must be free from bark. All 
old nests and rubbish should be burned, and the interior, especially 
crevices, sprayed liberally with kerosene. Boiling water or steam may 
be used instead of kerosene. A repetition of the procedure once every 
five or six weeks during the tick season is recommended. The use of 
considerable crude oil in and about the houses is very desirable. Fowls 
should not be permitted to roost in trees, because of the hiding places 
afforded the ticks beneath the bark, particularly when loose. 

If the henhouses can be made tight, fumigation with sulphur is 
useful, using about five pounds per 1000 cu. ft. of space. 

For the treatment of fowls infested with larval ticks, an ointment 
of kerosene, lard and sulphur is advised. 

Argas reflexus Fabr., commonly known as the " pigeon tick," differs 
from A. persicus in that the body narrows rather suddenly toward the 
anterior end and that the thin margin is flexed upward. The. capitu- 
lum has " two long post-hypostomal hairs ventrally, directed forwards. 
Palps with articles sub-equal, the third the shortest, denticulated hairs 
dorsally. . . . Hypostome rounded terminally, some small denticles 
at the tip, followed by f stout teeth merging into f to f progressively 
smaller teeth " (Nuttall). 

Other species of Argas are A. brumpti Neumann, A. vespertilionis 
Latreille and A. cucumerinus Neumann. 

Ornithodorus moubata Murray is the African relapsing fever tick 
(Fig. 200), sharing in part the characters of the genus Ornithodorus, 
viz. : " Body flat when unfed, but usually becoming very convex on 
distention. Anterior end more or less pointed and hood-like. Margin 



THE TICKS 



327 



thick and not clearly denned, similar in structure to the rest of the in- 
tegument, and generally disappearing on distention. Capitulum sub- 
terminal, its anterior portions often visible dorsally in the adult. Disks 
present or absent; but when present not arranged radially (see Argas). 
Certain fairly constant grooves and folds on the venter, namely, a 
coxal fold internal to the coxse, a supracoxal fold external to the coxse, 
a transverse pre-anal and a transverse post-anal groove or furrow, and 
a post-anal median groove. Eyes present or absent." 

0. moubata occurs only in Africa, is an eyeless species with a specific 
arrangement of the "humps " on the protarsus of the first pair of legs, 
being " subequal and tooth-like." The adults measure from 8 to 11 mm. 
in length and about 7 mm. in breadth. " The color varies from dusty 
brown to greenish brown in living specimens and turns reddish or 
blackish brown in alcohol." Eggs are deposited in small batches of 
from 10 to 80 at intervals of from three to 
fifteen days during a period of several months. 
The eggs are apparently readily deposited in 
captivity upon sand, as the writer has observed 
in other species of Ornithodorus. Hatching 
takes place in from ten to fifteen days and over, 
depending on temperature. Experimentally 
at least, the active larvae attach themselves to 
a warm-blooded host, remaining attached for 
nearly a week, when they become disengaged 
and molt, the nymph now appearing. The 
nymphs feed at intervals, molting once or 
twice between each meal ; there may be 6-9 
molts and apparently young females molt 
even after sexual maturity has been reached, according to various 
observers, and individuals may remain infective for over a year. Well- 
man has observed that this species attacks a wide range of animals 
besides man, notably pigs, dogs, goats and sheep ; Nuttall found them 
to feed in his laboratory on rabbits, mice, rats, monkeys and fowls. 

African Relapsing Fever is a disease of man occurring in Africa 
(Congo Free State, Angola and elsewhere), is caused by Spirochoeta 
duttoni Novy and Knapp and is therefore a Spirochetosis. The 
symptoms are described by Nuttall (1908, Joe. cit.) viz. : " headache, 
(especially at the back of the head), vomiting, abdominal pain and 
purging, with severe fever, a pulse of 90-120, dry hot skin, congested 
eyes and shortness of breath. After a period of fever lasting about two 
days, there is a fall of temperature, but a fresh attack soon follows. 
These relapses occur more frequently than in European relapsing fever, 
being usually 5 to 6 in number, but there may be more. The attacks 
leave the patient in a weak condition for a long time after recovery, 
which usually follows, but death occurs in about 6 per cent of the cases." 

Dutton and Todd in 1905 and R. Koch in the same vear showed 




Fig. 200. — African relaps- 
ing fever tick, Ornithodorus 
moubata. X 3. 



328 



MEDICAL AND VETERINARY ENTOMOLOGY 



that Ornitlwdorus moubata is a common and probably the usual carrier 
of this spirochete disease. Leishman as well as Nuttall has shown that 
the tick is infective only through its excreta and not by its bite, that the 
clear coxal secretion is an anticoagulant and non-infective. The 
infection is hereditary in the tick as in Texas cattle fever, and what is 
more the spirochete is transmitted to at least the third generation of 
ticks. The attack of fever takes place in the human in from 5 to 10 
days after the tick has bitten. 

Control. — Wellman's 1 recommendations, in part, to the govern- 
ment of Angola for the control of African relapsing fever are as follows : 
" (1) The tick in question should be regularly destroyed in crowded 
centers by disinfecting native houses, barracks and other permanent 
quarters, and by burning old camps, huts, etc. 

" (2) Soldiers, laborers on plantations, etc., should be made to keep 

their houses clean and to 
sleep in hammocks, or on 
beds well raised from the 
floor and away from the 
wall. Natives should 
never be allowed to sleep 
in or near the quarters of 
Europeans. 

" (3) Soldiers, porters, 
servants, plantation la- 
borers and other control- 
lable bodies of natives 
should be compelled to 
observe regulations re- 
garding regular bathing 
and washing of clothes. " 
The Spinose Ear Tick, 
Ornithodorus megnini Duges (Fig. 201), occurs commonly in California 
and other subtropical parts of the United States and Mexico. It re- 
ceives its name from the fact that the nymph is covered with numer- 
ous spines and in all stages the tick attacks the ears of cattle, horses, 
mules and occasionally other domesticated animals and man. Rather 
large dark eggs are deposited by this species on the ground, where 
the seed ticks hatch in two or three weeks (as short as eleven 
days according to Hooker). 2 Hooker furthermore states that the 
replete females creep upwards several feet before ovulation so that 
the larvae upon emerging find themselves in an advantageous position 




Fig. 201. — Spinose ear tick, Ornithodorus w.egnini. 
X3.5. 



1 Wellman, F. C, 1906. Human Trypanosomiasis and Spirochetosis in 
Portuguese South-west Africa with suggestions for preventing their spread in 
the colony. Journ. of Hygiene (Cambridge), Vol. VI, No. 3, pp. 237-245. 
» 2 Hooker, W. A., 1908. Life history, habits and methods of study of the 
Ixodoidea. Journ. of Econ. Ento., Vol. 1, No. 1, pp. 34-51. 



THE TICKS 329 

to reach the head and enter the ears of the host. The writer's observa- 
tions, however, indicate that the eggs are at least commonly deposited 
on the ground and that the larvae crawl up weeds and other vegetation 
as do other seed ticks and reach the host's head while grazing. The 
larvse feed in the deeper folds of the host's ears for from five to seven 
days, molting in situ, begin feeding again as nymphs, continuing their 
infestation for several weeks before leaving the ears. After the last 
molt, which occurs about seven days after leaving the host in mid- 
summer or early autumn, they begin depositing eggs. 

Damage Done. — The writer has received many complaints from 
various cattle grazing districts in California relative to the " ear tick." 
Ears are occasionally sent in thoroughly infested with these pests in 
all stages. It is commonly asserted that this tick is responsible for 
much deafness in domesticated animals, and it is also believed to be 
responsible for illness and even death, particularly in calves. 

Treatment. — Owing to the position occupied by the ticks on the 
host only local treatment is of any avail. Good results are ordinarily 
secured by flooding the ear with carbolated olive oil or linseed oil, which 
causes the parasites to vacate, whereupon they may be easily removed 
and destroyed by crushing or placing in kerosene. 

Other species of Ornithodorus. — Ornithodorus savignyi Audouin, 
occurs in Africa, is known as a venomous species and is believed to 
be a carrier of relapsing fever; Ornithodorus coriaceus C. L. Koch, 
known as the " Pajaroello," occurs in California and Mexico and is 
undoubtedly one of the most venomous species of ticks. (See Chapter 
XX.) 



CHAPTER XIX 
MITES 

Class Arachnida, Order Acarina 

Characteristics. — In the mites, as in the ticks, the abdomen is 
broadly joined to the cephalothorax with little or no evidence of separa- 
tion. All species are very minute, most of them just about visible to 
the naked eye. The mites have four pairs of legs as have other Arach- 
nids, but possess only three pairs (exceptionally less) as larvae. The 
mouth parts are more or less tick-like and are fitted for piercing. One 
or more pairs of simple eyes are usually present. The respiratory system 
is in most species similar to that of the ticks, i.e. tracheal. Nearly all 
species deposit eggs ; however, there are a few which are viviparous, 
among them Pediculoides. From the egg there emerges the hexapod 
larva, which molts shortly and then presents its fourth pair of legs. 
The life history of many species is passed in less than six weeks, in some 
as short as two weeks. 

An infestation of mites is termed acariasis. Those species which 
burrow into the skin, producing channels and depositing therein their 
eggs, are said to produce sarcoptic acariasis, e.g. Sarcoptes scabiei var. 
suis of swine mange; while those species which deposit their eggs at 
the base of the hairs of the host or on the skin and pile up scabs, are 
said to produce psor optic acariasis, e.g. Psoroptes communis var. ovis of 
sheep scab. 

A. Mange, or Itch Mites — Sarcoptic Acariasis 
Family Sarcoptida? 

Characters of Sarcoptidae. — All members of the family Sarcoptidse, 
commonly known as the itch mites, mange mites or scab mites, are very 
small (just about visible to the naked eye), whitish and somewhat 
hemispherical in form. Banks 1 characterizes this family, viz. : " The 
body is entire, and the surface transversely striated and provided with a 
few bristles, often short, stout and sharp-pointed. The legs are short 
and stout, arranged in two groups. The anterior legs are usually larger 
than the others. The tarsi commonly terminate in a stout claw. There 

1 Banks, Nathan, 1905. A treatise on the Acarina, or mites. Proc. U. S. 
National Museum, Smithsonian Institution, Washington, D.C., Vol. XXVIII, 
pp. 1-114. 

330 



MITES 



331 



is generally a long pedicellate sucker, sometimes with a jointed pedicel. 
The claw or sucker may be absent and in its place a long bristle. The 
legs often show a chitinous framework of rings, both transverse and 
oblique. On the front of the body is a prominent beak. The palpse 
are small, three- jointed and appressed to the sides of the beak beneath. 
. . . There are frequently sexual differences; some males have the 
third pair of legs very large and long, while the fourth pair is very small. 
Sometimes there are plate-like lobes at the tip of the male abdomen, 
and the tarsi may terminate differently in the two sexes." 

The family Sarcoptidse includes a number of important genera, 
among them Sarcoptes, Psoroptes, Chorioptes, Otodectes and Cnemi- 
docoptes. 

Mange or Itch Mites. — The mange or itch mites belong to the 
genus Sarcoptes, have very short legs, the posterior pair not extending 
beyond the margin of the nearly circular 
body (Fig. 202) ; suckers are present on 
the first and second pair of legs. The 
sarcoptic mites burrow in the skin, where 
they produce definite burrows in which 
the females deposit their eggs. 

The species of Sarcoptes inhabiting 
the skin of mammals are ordinarily termed 
varieties of Sarcoptes scabiei L., the dif- 
ferences being very slight and many of 
them may interchange hosts, e.g. Sarcoptes 
scabiei var. suis, parasitic on swine and 
on man, and when on the latter is known 
as S. scabiei var. hominis; Sarcoptes scabiei 
var. equi of the horse is also parasitic 
on man. Given parasites, however, ordi- 
narily exist only for a limited time on an- 
other host. 

Human Itch. — The itch mite attack- 
ing humans is known as Sarcoptes scabiei var. hominis. It attacks by 
preference the thin skin between the fingers, the bend of the knee and 
elbow, the penis and other parts of the body, producing an almost in- 
tolerable itching. Infestation is ordinarily secured by direct contact, 
hand shaking, etc. 

Life History of Itch Mite. — The female mites deposit their rather 
large oval eggs in the tortuous tunnels which they have made in the 
epidermis. From 10 to 25 eggs are deposited by each individual. 
" The female, having deposited her complement of eggs, dies at the end 
of her burrow. As the skin of the host is always wearing off, and 
constantly being renewed from below, the eggs, when ready to hatch, 
will be close to the surface, so that the mites may readily escape. Above 
each burrow there is often a little pimple, containing a watery fluid" 



•f 


Mb 




■ ^ 


It 


# 



Fig. 202. — Showing life history 
and general characteristics of a 
typical sarcoptic (mange or itch) 
mite ; egg (lower right) ; larva 
(lower left) ; male (upper left) ; 
female (upper right). Sarco-ptes 
scabiei var. suis, the itch or mange 
mite of swine. X 57. 



332 MEDICAL AND VETERINARY ENTOMOLOGY 

(Banks). The hexapod larvae hatch in three or four days. In this 
stage the area of infection is most rapidly increased. Maturity is 
reached in ten to twelve days, during which time there are said to be 
three molts. Gerlach, according to Braun, 1 has found that the progeny 
reproduce again in fifteen days, and that each female produces about 
fifteen individuals, after which she dies. Hence the descendants of 
one pair of mites in three months would number 1,500,000, which ac- 
counts for the rapid spread of itch on the individual host. 

Treatment of Human Itch. — Inasmuch as the mites are protected 
in their tunnels in the epidermis, the skin must be thoroughly softened 
with soap and hot water before a remedy is applied. Sulphur ointments 
give very good results if applied repeatedly at intervals of three or four 
days. Tar, creolin, balsam of Peru, tincture of iodine, etc., are also 
used. Underclothing coming in contact with the parts affected should 
be boiled. Cleanliness is essential to prevent infection. 

Swine Mange. — Mange of swine is caused by Sarcoptes scabiei var. 
suis (Fig. 202), which resembles Sarcoptes scabiei var. hominis very 
closely, if it is not identical. Mange attacks the swine commonly about 
the top of the neck, shoulders, ears, withers and along the back to the 
root of the tail. A microscopical examination of deeper tissue from 
beneath scabs will usually reveal the mites. Comparatively few cases 
of swine mange have come to the writer's attention, even in localities 
where swine raising is carried on extensively, hence it seems that the 
disease is not as widespread as might be expected. 

Suckling pigs and young shoats ordinarily suffer most. The affected 
animals scratch and rub vigorously, which may, however, be due to 
lice, but if the skin is cracked and thickly encrusted with heavy scabs, 
and the hair stands erect, an examination for scab mites should be made. 

Infected animals should be isolated and immediately treated, the 
quarters should be disinfected with a 10 per cent creolin solution, 1 to 
10 kerosene emulsion, 1 to 15 lime sulphur solution or the like. 

The life history and habits of the swine mange mite correspond in 
every respect with the itch mite of humans. 

Treatment for Swine Mange. — In the treatment of swine mange, 
it is necessary to apply external remedies, in addition to sanitary pre- 
cautions to prevent spread and reinfection of treated animals. 
Remedies are best applied in the form of solutions for the reason that 
all parts of the animal's body are thus easily reached in the dipping 
process. Hand dressing or scrubbing or the application of ointments 
may be practiced where dipping is not practical, but even so all parts 
of the animal should be thoroughly treated. 

Mayo 2 of the Virginia Polytechnic Institute recommends a "lime 

1 Braun, Max, 1908. The Animal Parasites of Man. (English Edition.) 
William Wood & Co. New York, xix + 453 pp. 

2 Mayo, N. S., 1910. Some diseases of swine. Bull. 189, Virginia Poly. 
Inst. Agr. Exp. Sta., 19 pp. 



MITES 333 

and sulphur" dip most highly. He uses S pounds of fresh lime and 24 
pounds of flowers of sulphur to 100 gallons of water, slaking the lime 
with sufficient water to form a thick paste, sifting in the sulphur and 
mixing with a hoe. This mixture is placed in a kettle with 25 to 30 
gallons of water and boiled for one hour at least, two hours being better. 
Mayo suggests using the entire mas- for swine, which must not, however, 
be done for sheep. The dip is used warm at a temperature of from 
100° to 110 c F. This temperature may be maintained by running a 
steam pipe along the bottom of the dipping vat. 

Prepared '"lime and sulphur" dips can be secured readily on the 
market, and are commonly used at the rate of one part of the solution 
to fifteen parts of water, however, care should be exercised to use the 
dip as directed, owing to variation in constituents. Coal tar dips are 
also used extensively and give good results if used properly. 

Dipping vats may be made of wood or concrete and are usually -et 
in the ground at a slight elevation to insure drainage away from the 
vat. A convenient size for a vat is *" ten feet long on top, eight feet 
long on the bottom, one foot wide on the bottom and two feet wide at 
the top. The end where the hogs enter should be perpendicular and the 
other end inclined, with cleats, so that the hogs can emerge after passing 
through. The entrance should be by a slide. For pigs and small 
shoats that can be easily handled, a barrel serves the purpose well ; the 
pigs can be caught, plunged in the dip and held there the required time. 
Some successful swine raisers build cement bathing places or wallows 
for swine and keep these filled with a watery solution of some dip or 
disinfecting solution. If -wine have wallowing holes filled with water, 
some of the good dips should be put in these frequently." The time to 
treat young pigs, and this is important, is at weaning time. Dipping 
twice as for older animals is necessary, and by placing them in unin- 
fected quarter- they ought to remain clean. 

Mangy swine should be hand dre--ed with a stiff brush before dip- 
ping in order to loosen up scabs, and then kept in the dip long enough to 
permit the solution to soak through the scabs, certainly not less than 
two minutes. All the animals must be dipped a second time in eight 
or ten days in order to destroy the mites which have hatched from the 
eggs which are not destroyed. 

Mayo (1910, loc. cit.) recommends a disinfecting whitewash to be 
applied to pens, etc.. viz.. " Fresh lime. 25 pounds, flowers of sulphur, 
15 pounds, mix the sulphur with a little water, to a paste, add 30 gal- 
lons of water and cook for an hour, then add water sufficient to make 
50 gallons and apply with a spray pump, using a ' Bordeaux ' nozzle." 

Equine Mange. — Sarcoptic aeariasis in horses, mules and ass 
is caused by Sarcoptes scabiei var. equi. This species is also transmis- 
sible to man and is said to be the chief cause of the itch of cavalrymen 
and others handling horses extensively. Infestations on humans only 
last for two or three weeks. 



334 MEDICAL AND VETERINARY ENTOMOLOGY 

The most reliable diagnostic character is the discovery of the mite, 
which is accomplished as in swine mange. The usual symptoms * 
are first of all a strong tendency to rub some circumscribed part such as 
the head, root of the mane or tail, withers or back, due to an incessant 
itching. If a person scratches the affected parts, the animal moves its 
lips as though it were nibbling. The skin of these parts also shows an 
eruption of " fine conical papillae." The hair here stands erect and bristly, 
many having dropped out, but totally bare spots in which there are no 
isolated hairs apparently do not occur in mange, but do in ringworm 
according to Law. The affected parts are at first scurfy, then become 
covered with yellowish scabs, which latter exude matter due to the 
rubbing and inflammation, and finally there are formed scabs and crusts, 
often with deep crevices. During the first fourteen days the progress 
of the disease is usually slow, but by the sixth week the ravages of 
the disease become extensive and there is rapid progress. 

The life history and habits of Sarcoptes scabiei var. equi correspond 
in every respect with other species already described. 

Treatment of Equine Mange. — Before applying a local remedy for 
mange it is necessary to clip the entire animal so as to disclose all points 
of attack which might otherwise be hidden by hair. The clipped 
hair must not be blown by the wind and should be burned. The 
parts affected are next thoroughly lathered and left for a short while 
to soften, after which warm water is applied and the scabs rubbed off 
as far as possible with wisps of hay or straw and these also burned. 
The affected parts are now ready for a parasiticide, which must be 
applied by hand. 

Many remedies may be had for mange, all of which have more or less 
virtue, but the writer has found that those containing sulphur have the 
greatest virtue. The ordinary "lime and sulphur" sheep dips applied 
locally and thoroughly, repeated three or four times at intervals of five 
days, ordinarily prove effective. Among other remedies Law (1905, 
loc. cit.) recommends creosote, 5 parts, alcohol, 5 parts, water, 25 parts ; 
to be rubbed in thoroughly two or three times at intervals of from three 
to five days. The application of a 2 per cent solution of Chloronaph- 
tholeum applied as above proves very satisfactory, as does Kreso dip, 
one to forty. 

Stalls in which mangy horses have been kept must be disinfected 
with live steam or boiling water or mercuric chloride one part to 500 of 
water. If the latter is used its very* poisonous properties must be 
considered. Brushes, scrapers, rubbers, etc. must be boiled; harness 
must be rubbed thoroughly with a strong disinfectant, for example 
2 per cent formaldehyde, or Chloronaphtholeum. 

Bovine Mange. — Sarcoptic acariasis, or mange, in cattle is said to be 
rare ; however, the psoroptic form (scabies) is quite common. 

1 Law, James, 1909. Textbook of Veterinary Medicine. Vol. V., 621 pp. 
Ithaca, N.Y. 



MITES 



335 



Canine Mange. — Mange of dogs is caused primarily by Sarcoptes 
scabiei var. canis, closely resembling the swine variety. Mange in the 
dog appears first on the muzzle, around the eyes, on ears and breast 
and later spreads to the back, abdomen and elsewhere. Symptoms are 
much as in swine and horses. Canine mange is evidently transmissible 
to humans. 

Treatment for Canine Mange. — Long-haired dogs must be clipped 
before applying a remedy. Law recommends the following treatment : 
" the whole skin may be covered with a solution of equal parts of green 




Fig. 



203. — Showing (a) normal leg and claw of a fowl and (6) one affected with sar- 
coptic mites, Cncmidocoptes ?nutans, causing scaly leg. 



potash soap and alcohol and just enough carbolic acid to give it the 
odor. This is washed off next day and the surface is covered with the 
following : Naphthalin, | oz., vaseline, 2 oz., or alcohol 1 pint makes a 
most agreeable, if somewhat expensive, dressing, which, though slow, 
is effective. Creolin, 1 part, in alcohol, 15 parts, is very efficient." 
Tobacco, carbolic acid and other poisons which may be licked off by 
the dog should not be used, unless a tight muzzle is provided. 

Other Mange Mites. — Mange of cats is said to be caused by Sar- 
coptes minor var. felis, mange of goats by Sarcoptes scabiei var. capr&, 
and of camels by Sarcoptes scabiei var. cameli. 

Scaly Leg Mite of Poultry. — The legs of domestic fowls (chickens, 
turkeys, pheasants, etc.) are frequently covered with heavy scales and 
incrustations (Fig. 203). This condition is produced by a burrowing 
mite (Fig. 204), Cnemidocoptes (Sarcoptes) mutans Robin. The mites 



336 MEDICAL AND VETERINARY ENTOMOLOGY 



burrow and live in the skin, depositing their eggs in these channels as 
do the mange mites. Scaly leg is easily transmitted from fowl to fowl, 
hence the infested birds should be isolated and treated. 

Treatment of "Scaly Leg." — The legs must be soaked and manipu- 
lated with the hands in soap and warm water in order to soften the scabs. 
Then when dry, " apply a coating of balsam of Peru, or an ointment 
containing 2 per cent of carbolic acid " or " a mixture of one part of oil 
of caraway with five parts of vaseline " (U. S. Dept. of Agr., Farmers' 
Bull. 530). The writer has repeatedly recommended dipping the legs 




rfff-- 



B 



Fig. 204. — (a) Photograph of a portion of scale from a fowl affected with "scaly leg," 
showing mites (Cnemidoc<yptes mutans) in situ; (b) enlargement of an individual 
mite. X 170. 

of the fowl in a vessel containing 1 part kerosene and 1 part linseed oil ; 
the oil must not touch the feathers on the leg otherwise the skin may 
suffer. This dipping process is best done while the birds are roosting, 
lifting each bird from the roost, dipping and then replacing it. The 
process should be repeated in not over a week. 

Depluming Mite. — Cnemidocoptes gallinoe Railliet, known as the 
depluming mite, is closely related to the " scaly leg mite," but attacks the 
skin of the fowl near the base of the feathers. The mites themselves do 
not cause the bird to lose its plumage, but the intense itching caused 
by the mites impels the host to pluck its feathers in an attempt to reduce 
the itching. 

Dipping the birds in a 2 per cent solution of creolin, or in a 2 per 
cent solution of Zenoleum, or rubbing the skin with a sulphur ointment 
will, if the treatment is repeated, relieve the trouble considerably. 



MITES 



337 



B. Scab Mites — Psoroptic Acariasis 
Family Sarcoptidce 

Characteristics of Psoroptic Mites. — The psoroptic or scab mites 
belong to the family Sarcoptidce as do the itch and mange mites, hence 
partake of the family characteristics. However, in the psoroptic mites 
the legs are long and slender, all four pairs extending beyond the margin 
of the body which is elongate (Fig. 205). The " pedicel of the suckers 
is jointed " and the " mandibles styliform, serrate near tip " and suited 
for piercing. The psoroptic mites do not burrow, as do the sarcoptic 




Fig. 205. — Showing life history and general characteristics of a typical psoroptic or scab 
mite. Egg (lower left) ; larva (lower right) ; male (upper right) ; female (upper left). 
Psoroptes communis var. equi of the horse. X 85. 

mites, but live at the base of the hairs of the host, piercing the skin, 
causing an exudate which partially hardens, forming scabs which pile 
up as a crust of loose humid matter. This condition is known as scabies 
or scab. Among the piled up scabs are deposited the eggs. Owing to 
the loose condition of the scabs and the hardihood of the mites, this 
form of acariasis becomes quickly and easily distributed from animal 
to animal by contact and by rubbing against fences, trees, and the like. 
The commonest scab mites belong to the genus Psoroptes of which 
Psoroptes communis var. ovis of the sheep is best known. Other varieties 



338 MEDICAL AND VETERINARY ENTOMOLOGY 

of this species infest cattle and horses mainly. Several species of psorop- 
tic mites attack the ears of cats and dogs, Otodectes cygnotis Gedoclst. 

Ovine Scabies (Sheep Scab) Psoroptes communis var. ovis (Fig. 
206) is the causative organism of scabies in sheep. This is by far the 




Fig. 206. 



Sheep scab mite, Psoroptes communis var. ovis, 
X75. 



male (left) ; female (right) . 



most important species of scab mite. However, with the widespread 
use of dips, and rigid quarantine regulations, scabies in sheep is grad- 
ually being controlled. 

The sheep scab mite is easily visible to the naked eye. The adult 
female measures about "one fortieth" of an inch in length by "one- 
sixtieth" of an inch in breadth, and the male "one-fiftieth" by "one- 
eightieth" of an inch. As in all psoroptic species the mites are found 
on the surface of the body among the scabs at the base of the hairs. 

The parts of the body most 
thickly covered with wool are 
chiefly affected. 

Symptoms of Sheep Scab. 
— Scabies is first indicated 
by a slight "tagging" of the 
wool, the coat becomes rough, 
ragged and matted at the 
points affected (Fig. 207). 
Tags of wool are torn away 
by the sheep or are left at- 
tached to rubbing posts and 
other objects against which 
the animal rubs. The sheep 
scratches vigorously and 
shows signs of intense itching. ' The skin of the affected part is covered 
with yellowish papules of varying size, and a marked accumulation of 




Fig. 207. 



An advanced case of sheep scabies. 



MITES 339 

scurf among the roots of the wool. Later the affected skin swells uni- 
formly, and the increasing exudation concretes into a massive scab en- 
veloping the roots of the wool, so that as it increases layer by layer on 
its deeper surface, it lifts the fibers out of their follicles, detaching the 
wool and leaving extensive bare scabby patches. The denuded surface 
shows all the variation of lesions shown in other mangy animals. Pap- 
ules, vesicles, pustules, scabs, cracks, excoriations, and even sloughs 
may appear at different points. Sometimes in clipped sheep the exudate 
forms a uniform, smooth, parchment-like crust covering the whole ex- 
posed area. Around these bare patches the wool is encrusted at its roots, 
or shows a dark, dirty, scurfy layer composed of epidermic cells, yolk, 
dried exudate and the exuviae of the acarus. Beneath this the parasite is 
found in myriads. The bare spots may show comparatively few " (Law) . 

Life History of the Scab Mite. — The female scab mite deposits 
an average of about 15 (maximum 30) eggs, one at a time, and the 
period of oviposition often lasts several days, when the female evi- 
dently dies. The eggs are either attached to the wool near the skin 
or deposited directly upon the latter. The hexapod larvae hatch in 
from three to seven days, the first molt taking place in three or 
four days when the fourth pair of legs appears ; a second and third 
molt takes place within the next four or five days. Sexual maturity 
is evidently reached about the time of the second molt. Although 
there is considerable variation in the length of time elapsing from egg 
to egg, twelve to fourteen days is ordinarily accepted as an average. 

Treatment for Sheep Scab. — Internal remedies, such as sulphur, 
have been found to be unsuccessful by the U. S. Department of Agri- 
culture. However, sulphur applied externally in the form of " lime and 
sulphur " dip has been used for many years as a successful remedy. 
Several kinds of dips with variations are commonly used against sheep 
scab, among them, lime and sulphur, tobacco and sulphur, tobacco, cresol, 
coal tar products, Chloronaphtholeum, Kreso, etc. If proprietary dips 
are used, extreme care must be exercised in following the directions. 
The dip should have the approval of the U. S. Department of Agricul- 
ture. All dips must be repeated in seven or eight days and not later 
than ten days in order to destroy the mites newly hatched from eggs, since 
very few dips, except perhaps creosote dips, are injurious to the eggs. 

Lime and Sulphur Dips. — Experience in many sheep-raising dis- 
tricts has proved that lime and sulphur dips are most efficient in the 
control of scab, if properly used. Damage to the wool, if dipping is 
done shortly after shearing, is very slight indeed. If there is any 
doubt, or injury has been produced in the use of lime and sulphur, other 
dips are available, notably nicotine. 

Among the varieties of lime and sulphur dips mentioned by the U. S. 
Bureau of Animal Industry x are the following : 

1 Salmon, D. E., and Stiles, Ch. Wardell, 1903. Scab in Sheep. U. S. Dept. 
Agr. Farmers' Bull. No. 159, 45 pp. 



340 MEDICAL AND VETERINARY ENTOMOLOGY 

1. For fresh scab (U. S. B. A. I. formula) : 

Flowers of sulphur 24 lbs. 

Unslaked lime 8 lbs. 

Water 100 gals. 

2. For very hard scab (Fort Collins formula) : 

Flowers of sulphur 33 lbs. 

Unslaked lime 11 lbs. 

Water 100 gals. 

'6. For unusually severe cases (Nevada formula) : 

Flowers of sulphur 16f lbs. 

Lime 33| lbs. 

Water 100 gals. 



According to the U. S. Bureau of Animal Industry " thirty-three 
pounds of lime to one hundred gallons of water is the largest proportion 
admissible under any circumstance." 

How to Prepare Lime and Sulphur Dip. — Much time may be saved 
by purchasing the lime and sulphur already prepared and using it as 
directed, but the mixture may be prepared as follows, as directed by the 
United States Department of Agriculture : 

"A. Take 8 to 11 pounds of unslaked lime, place it in a mortar 
box or a kettle or pail of some kind, and add enough water to slake the 
lime and form a " lime paste " or " lime putty." 

Many persons prefer to slake the lime to a powder, which is to be 
sifted and mixed with sifted sulphur. One pint of water will slake three 
pounds of lime, if the slaking is performed slowly and carefully. As a 
rule, however, it is necessary to use more water. This method takes 
more time and requires more work than the one given above, and does 
not give any better results. If the boiled solution is allowed to settle, 
the ooze will be equally as safe. 

" B. Sift into this lime paste three times as many pounds of flowers 
of sulphur as used of lime, and stir the mixture well. 

Be sure to weigh both the lime and the sulphur. Do not trust to 
measuring them in a bucket or to guessing at the weight. 

" C. Place the sulphur lime paste in a kettle or boiler with about 
25 or 30 gallons of boiling water, and boil the mixture for two hours at 
least, stirring the liquid and sediment. The boiling should be con- 
tinued until the sulphur disappears, or almost disappears, from the sur- 
face ; the solution is then of a chocolate or liver color. The longer the 
solution boils the more the sulphur is dissolved, and the less caustic the 
ooze becomes. Most writers advise boiling from thirty to forty minutes, 
but the Bureau obtains a much better ooze by boiling from two to three 
hours, adding water when necessary. 

" D. Pour the mixture and sediment into a tub or barrel placed near 
the dipping vat and provided with a bunghole about four inches from 
the bottom and allow ample time (two to three hours, or more if neces- 
sary) to settle. 

The use of some sort of settling tank provided with a bunghole is an 



MITES 341 

absolute necessity, unless the boiler is so arranged that it may be used 
both for boiling and settling. An ordinary kerosene oil barrel will 
answer very well as a small settling tank. To insert a spigot about 
three to four inches from the bottom is an easy matter. Draining off 
the liquid through a spigot has the great advantage over dipping it out, 
in that less commotion occurs in the liquid, which therefore remains 
freer from sediment. 

" E. When fully settled, draw off the clear liquid into the dipping vat 
and add enough warm water to make 100 gallons. The sediment in 
the barrel may then be mixed with water and used as a disinfectant, but 
under no circumstances should it be used for dipping purposes." 

The Dipping Vat. — Dipping vats may be constructed either of wood 
or of concrete, should be about nine inches wide at the bottom, two feet 
six inches at the top, about 5 feet deep, and thirty-five to forty feet in 
length. The entrance end is built steep while the exit end has a gradual 
slant provided with cleats. 

How to Proceed. — The sheared sheep are driven into the receiving 
pan, the dip having been prepared in the meantime and warmed to 
102° to 105° F. One after another the sheep are forced into the dip, in 
which they must be kept two minutes and the head drenched at least 
once while traveling toward the exit end of the vat (see Fig. 208). 
From the vat the sheep emerge in dripping pens. 

Tobacco Dips. — Tobacco (nicotine) dips are now used very exten- 
sively with excellent results. Tobacco dips are used either with or 
without sulphur. Owing to variation in nicotine content, homemade 
dips or proprietary tobacco dips are not safe unless the percentage is 
ascertained. When diluted ready for use the nicotine content must be 
.07 of one per cent, — a requirement of the Bureau of Animal Industry. 

After a very careful and rigid experiment conducted by the Kentucky 
Agricultural Experiment Station x in cooperation with the Bureau of 
Animal Industry with reference to the addition of sulphur, the follow- 
ing conclusions were reached : 

" With the conditions under which this experiment was carried on, 
as given in this bulletin, the addition of flowers of sulphur in the pre- 
scribed dilutions of nicotine did not, as far as could be discerned, enhance 
the value of these dips in curing sheep of the disease of scabies. 

After the conclusion of the above experiment, dippings were con- 
ducted by the Bureau of Animal Industry on the western ranges under 
field conditions. The results were confirmatory to the conclusions 
drawn from the above experiments and a ruling was made by the Bureau, 
taking effect May 1, 1911, withdrawing the requirement that sulphur 
be added to tobacco dips. The ruling requires that seven-hundredths 
of one per cent of nicotine be used at each dipping." 

1 Good, Edwin S., and Bryant, Thomson R., 1911. The dipping of sheep 
for scabies in tobacco dips with and without the addition of flowers of sulphur. 
Kentucky Agr. Exp. Sta. Bull. 157, pp. 183-193. 



342 MEDICAL AND VETERINARY ENTOMOLOGY 






Fig. 208. — Dipping sheep, (a) plunging the sheep into the vat ; (6) sheep swimming 
through the vat ; (c) sheep emerging from the vat ; (d) entering the pens after emerg- 
ing from the vat. (Photo by G. P. Gray.) 



MITES 343 

The second dipping in the above experiment was given in ten days 
and the temperature of the water was 105° F. 

A tobacco extract containing 2.9 per cent nicotine must (according 
to the above bulletin) be diluted with 56.85 gallons of water to produce 
.07 per cent nicotine dip, or 80.14 gallons of water for a .05 per cent nico- 
tine dip. Nicotine sulphate (about 40 per cent nicotine) must be 
diluted with 86.17 gallons of water for .07 per cent nicotine or 120.70 
gallons for a .05 per cent solution. 

If sulphur is used with tobacco, 16 pounds of flowers of sulphur are 
required per 100 gallons of water. The sulphur is made into a thin paste 
with water before adding it to the dip. 

Other Dips Used for Sheep Scab. — Great care should be exercised 
in selecting proprietary sheep dips ; many are unreliable and result in 
waste of money, time and energy. The carbolic acid dips vary consid- 
erably in their cresol content even in packages sold under the same label. 
At all events use the dip exactly as recommended. Among the more 
widely used dips other than those mentioned above are Kreso, used 
1 to 72, Zenoleum, 1 to 50, and Chloronaphtholeum, 1 to 50. The rat- 
ing of the U. S. Bureau of Animal Industry should govern the choice of 
the remedy. 

Bovine Scabies. — Scabies in cattle is caused by Psoroptes communis 
var. bovis and is comparatively common. The disease usually appears 
at the root of the tail, thighs, neck and withers and spreads rapidly to 
other parts of the body. 

Treatment for scabies in cattle is most successfully undertaken with 
tobacco sulphur dips or lime and sulphur dips. The former is used as 
in sheep scab, while in the latter twelve pounds of unslaked lime and 
twenty-four pounds of flowers of sulphur to one hundred gallons of water 
are used. 

The following general directions are given by the South Dakota 
Agricultural Experiment Station : x 

" 1. The temperature of the dipping vat should be constantly main- 
tained at from 103° F. to 105° F. 

" 2. Animals badly affected are preferably to be hand dressed by 
scrubbing the scabby areas with a stronger solution of the dip. When 
lime and sulphur is used this has the effect of softening the firm scab, 
allowing the dip to penetrate. 

"3. Each animal should be held in the vat for two minutes, and 
completely immersed twice. 

" 4. All animals that have been in contact with the diseased ones 
should be regarded as infected and dipped. 

"5. The dipping should be repeated in from ten to fourteen days to 
destroy the parasites that may have hatched out subsequently to the 
first dipping. 

1 Moore, E. L., 1911. Scabies (Mange) in Cattle. Agr. Exp. Sta. South 
Dakota State College of Agr. and Mech. Arts, Bull. 131, pp. 203-216. 



344 MEDICAL AND VETERINARY ENTOMOLOGY 



"6. Dipped cattle should not be returned to infected stables or 
corrals." 

Equine Scabies. — Scabies of horses and mules is traceable to 
Psoroptes communis var. equi (Fig. 205) . This variety is also known as 
the " long-nosed Psoroptes." Owing to the confluent sores, exudate, and 
smooth surface where scabs have been rubbed off this disease is also 
known as " humid mange." The mites are more easily discovered than 
in sarcoptic acariasis, and owing to the more exposed condition of the 
organisms the disease is easier of control. 

Treatment of Equine Scabies does not differ materially from mange. 
Therefore the usual preliminary treatment with soap and water is 
pursued, followed with a parasiticide. Law strongly recommends 

. —^ Roll's formula of tar and sulphur \ lb. each, 

green soap and alcohol, 1 pound each. The 
usual disinfection of stalls, harness, brushes, etc., 
mmk must be pursued. 

wk Mites in Ears of Rabbits, Cats and Other 

Animals. — A comparatively common affection 
of domesticated rabbits, also of cats and dogs, 
r is known as otacariasis or parasitic otitis and is 

traceable to Symbiotes auricularum Railliet or 
Otodectes cygnotis Gedoelst, resembling Psoroptes 
very closely. The mites literally swarm in the 
ears of their host, causing much discomfort, 
tenderness of the ears, auricular catarrh, loss of 
appetite, wasting, torticollis, etc. 

Cleansing the ears first with soapsuds and 
warm water, and then applying a sulphur oint- 
ment or a 10 per cent solution of tincture of iodine 
in glycerine, or a 1 per cent solution of carbolic 
acid in linseed oil is recommended. The hutches 
or kennels must be thoroughly disinfected with a strong lime and sul- 
phur solution or carbolic acid to prevent further contagion. 



Fig. 209. — A follicle mite 
Demodex folliculorum 
X 110. 



C. Follicle Mites — Follicular Mange 
Family Demodecidce 

Characteristics of Follicle Mites. — The Demodecidse include very 
minute (.3-4 mm.) mites with elongated transversely striated abdomen 
and possessing four pairs of " stubby " three-jointed legs (Fig. 209). 

The follicle mite (Demodex folliculorum Simon) inhabits the hair 
follicles and sebaceous glands of men and other mammals " causing 
inflammation of the gland (comedones) ; their agglomeration in the 
meibomian glands (in man) sets up inflammation of the margins of the 
eyelids" (Braun). While the follicle mites may, under certain condi- 



MITES 345 

tions, produce acne-like conditions, it is hardly probable that many cases 
of " blackhead " if any, may be traceable to these mites. They are 
nevertheless very common, — said to occur in 50 per cent of mankind 
in all parts of the world. 

The variety found in man is known as Demodex folliculorum var. 
hominis; that of the dog as Demodex folliculorum var. cards; of the 
sheep var. ovis; of the ox, var. bovis ; of swine, var. suis, etc. 

In most animals the follicle mites are found in the region of the 
muzzle and the affection is known as follicular mange, manifested by a 
reddish raw appearance. According to Banks (1905, loc. cit.) Demodex 
bovis Stiles has been recorded from hides of American cattle in which 
swellings about the size of a pea were formed on the skin. In these 
swellings great numbers of the mites occurred. The value of the hides 
is said to be lessened to a considerable degree. 

Owing to the fact that the follicle mites occur so deeply in the skin, 
treatment is made very difficult. Penetrating materials are necessary, 
for example, benzine, 1 part, and olive oil, 4 parts, or applications of tinc- 
ture of iodine. Frequent applications must be made until a cure has 
been effected. 

D. Harvest Mites or Chiggers 

Family Trombidiida? 

Characteristics. — Members of the family Trombidiidse are com- 
monly known as ''harvest mites," " jiggers," or "red bugs." In Mexico 
they are known as " Tlalsahuate." According to Banks they " are recog- 
nized by the body being divided into two portions, the anterior (ceph- 
alothorax) bearing the two anterior pairs of legs, the palpi, mouth parts 
and eyes ; the posterior (abdomen) is much larger and bears the two 
posterior pairs of legs. The mandibles are chelate, at least there is a 
distinct jaw or curved spine-like process. They are always red in color, 
some, however, being much darker than others. The body is covered 
with bristles or feathered hairs according to the species. The palpi 
are five-jointed, quite prominent, often swollen in the middle, the penul- 
timate joint ending in one or two claws, the last joint (often clavate) 
appearing as an appendage or tl thumb " to the preceding joint. The 
legs are seven- jointed ; the tarsi terminate in two small claws. The 
legs are clothed in the same manner as the body. There are two eyes 
upon each side of the cephalothorax, quite frequently borne on a distinct 
pedicel." 

The most important genus affecting man is Trombidium, of which 
the larval form is known as Leptus (Fig. 210), e.g. Leptus autumnalis 
Shaw. Among the species of Trombidium are T. holosericeum Say, 
T. magnificum, Lee, etc. 

Habits and Life History. — In the free-living adult stage the Trom- 
bidiidse feed on insects and do not attack warm-blooded animals ; the 




346 MEDICAL AND VETERINARY ENTOMOLOGY 

newly emerged larvae at once become parasitic on grasshoppers and 
other insects, where they become full grown, molt and mature. In this 
stage (the larval) the mites also attack humans and other warm-blooded 
animals, but perish in the act of burrowing into the skin. Owing to the 
fact that the mites are so abundant during the autumn they are com- 
monly called " harvest mites." Their chief habitat is among the weeds 
and tall grass in neglected pastures, among blackberry bushes and the 
like. The individuals which succeed in reaching maturity overwinter 

and deposit large numbers of eggs on 
the ground in sheltered weedy spots; 
these hatch in summer and autumn. 
There seems to be but one generation 
a year. 

During midsummer and autumn 
it is almost impossible to traverse a 
mite-infested pasture without suffering 
an attack of intense itching about the 
ankles and up to the knees within a 
few hours. The mites are believed 
to enter the skin either through the 
Fig. 210. — Chigger mite or harvest pores, hair follicles, or even directly. 
mite ; — larva (Leptus) of Trombi- There are formed red blotches often 

of considerable size and the itching is 
just about unbearable. Water blisters of larger or smaller size (1 to 
5 mm. and over) appear in a day or two after itching begins. 

Treatment for Harvest Mites. — The extreme irritation occasioned 
by these mites may be relieved considerably by bathing, using soap 
freely, followed by sponging with a weak solution of carbolic acid (an 
ounce to a quart of water), weak ammonia, soda solution, or alcohol, 
or anointing the affected spots with an ointment or salve containing 
sulphur. Rubbing the skin with tobacco water, benzine, kerosene, or 
glycerine is also suggested as a remedy, also as a preventative to persons 
rinding it necessary to work in regions when the jiggers or red bugs are 
in season. Clearing infested spots of weeds, shrubbery, and tall grass 
is necessary to control the mites. 

E. The Poultry Mite 

Family Gamasidce 

Gamasid Mites. — The family Gamasidse includes a large number 
of species parasitic mainly on birds and insects. The group is some- 
times elevated to the rank of a superfamily (Gamasoidea) and then 
includes three families, viz., Dermanyssidse, Gamasidse and Uropodidse. 
The close structural relationship of at least the first two hardly justifies 
this separation. 



MITES 



347 



From our viewpoint the most important member of the family Gama- 
sidse (or Dermanvssidse) is the poultrv mite, Bermanyssus gallincB Redi 
(Fig. 211). 

Damage Done. — The poultry mite is one of the worst enemies of the 
poultry raiser in the Southern states and in California, and is evidently 
a serious pest in many other parts of the world. The damage which 
this mite produces is very considerable and may be summarized as 
follows : egg production is greatly reduced or entirely prevented as 
shown by Repp 1 ; sitting hens are often caused to leave their nests or 
perish; newly hatched chicks perish in 
great numbers in the presence of these 
mites ; chickens lose flesh, are unthrifty, 
and are unprofitable for marketing ; loss 
of blood and reduced vitality produce 
birds easily susceptible to disease. 

Habits and Life History. — In size 
the mites vary from .6 to .7 mm. in length, 
are somewhat pear-shaped and are light 
gray when unengorged and from light to 
a dark red when engorged. 

During the daytime the mites remain 
hidden in the crevices of the henhouse, 
under the roosts, under boards, etc. In 
these hiding places the eggs are deposited. 
At night the little pests swarm out from 
their hiding places and attack the fowls 
upon the roosts. Their attack on the 
fowls is, however, not restricted alto- 
gether to the night, but swarms of them 
may be found on sitting hens and lay- 
ing hens during the day while nesting in 
darker situations. 

Myriads of tiny eggs are deposited in all sorts of crevices. The six- 
legged larvae hatch in four to six days, feed largely on filth at first and 
later attack the chickens, as do the adults. Full growth is reached in 
from three to six weeks, depending on temperature. Some authors give 
the time for development at from ten days to two weeks. There are 
three or four molts before sexual maturity is reached. 

Control of the Poultry Mite. — Above all things extreme cleanliness 
and plenty of sunlight are necessary to prevent rapid multiplication. 
Kerosene emulsion (one part to ten parts of water) applied with a spray 
pump to all parts of the henhouse, particularly the crevices, has been 
found most serviceable in destroying the mites. The spray must be 
repeated in about Hve or six days to kill the mites hatching from the eggs, 
which latter are not injured by the spray. 

1 Repp. John J., 1903. The chicken mite. Iowa State College Exp. 
Sta. Bull. 69, pp. 287-294. 




Fig. 211. — The poultry mite, Dcr- 
manyssus gallince. X 45. 



348 MEDICAL AND VETERINARY ENTOMOLOGY 

It is well to remove all roosts and paint these with kerosene or gaso- 
line, daubing the ends abundantly with tar or crude oil before replacing. 

Straight kerosene applied with a spray pump as directed for the 
chicken tick proves very effective, if repeated two or three times at inter- 
vals of five or six days. 



F. Louse-like Mites 

Family Tarsonemidce 

Characteristics of Tarsonemidae. — This is a small family of soft- 
bodied mites having in the female a characteristic " prominent clavate 
organ of uncertain use " between the first and second pairs of legs 
(Fig. 212). The third and fourth pairs of legs are separated from the 
first and second pairs by a long interspace. There is present a consid- 
erable sexual dimorphism in the several species. The piercing, sucking 
mouth parts are provided with slender needle-like 
;| stylets. Many of the species are predaceous or para- 
^ sitic, while others suck the juices of certain plants. 

Pediculoides ventricosus Newport is a widely dis- 
Jb tributed predaceous mite which attacks the larvae of 

a number of species of insects such as the Angou- 
jfM B| l mois grain moth (Sitotroga cerealella Oliv.), the wheat 

M mm joint-worm (Isosoma tritici Fitch), the peach twig 

borer (Anarsia lineatella Zell.), the cotton-boll weevil 
Br (Anthonomus grandis Boh.), etc. It is therefore 

normally a beneficial mite, but unfortunately it 
also attacks man, producing a very disagreeable 
dermatitis. 

While the male mite is very tiny, just about 
visible to the naked eye, the female when pregnant 
becomes enormously swollen, measuring nearly a millimeter in length, 
the abdomen presenting a globular appearance, the cephalothorax and 
appendages barely visible. 

Within the enlarged abdomen of the female may be found rather 
large eggs which hatch internally, and the young mites develop to 
maturity within the body of the mother before being extruded. The 
number of young produced by the female is said to range from a few to 
nearly 300. 

A number of epidemics of dermatitis have been traced to these mites, 
infection having been brought about by sleeping on straw mattresses 
or while laboring in grain fields at harvest time. The infection has been 
confounded with hives, scabies and even chicken pox and smallpox, 
and appears on the neck, chest, abdomen, back, arms, and legs, in fact 
the whole body may be involved and the itching is very intense. The 
eruption is commonly accompanied with fever as high as 102° F. 



Fig. 212. — A louse- 
like mite, Pedicu- 
loides ventricosus. 
X32. 



MITES 



349 



According to Goldberger and Schamberg 1 the itching subsides under 
continuous exposure in from 3 to 7 weeks. They also recommend treat- 
ing the affection with an ointment of beta naphthol, sulphur, benzoate 
and lard. 

To destroy mites in the straw of mattresses or in other situations, 
fumigation with sulphur or formaldehyde gas or steaming is recom- 
mended. 

As to prevention Webster 2 suggests burning the grain stubble dur- 
ing the fall, winter or spring, also that threshing direct from the shock 
resulted in the control of the grain moth and consequently of the para- 
sitic mites. 



G. Flour and Meal Mites — Grocer's Itch 
Family Tyrogliphidce 

Characteristics of Tyrogliphidae. — This family includes a small 
group of very tiny mites, ordinarily about 0.5 mm. or less in length. 
Several of the species attack grain, 
flour, meal, dried meat, hams, dried 
fruits, insect collections, etc. Their 
development is so rapid that there 
may be literally millions of them in 
some stored products in a few days. 

The metamorphosis of this group 
involves a peculiar stage known as 
the Hypopus, appearing after the lar- 
val and nymphal stages, very unlike 
either of these and very different 
from the adult. This stage is said to 
attach itself, non-parasitically, to 
flies and other insects, which serve 
as disseminators of the mites. 

Persons handling stored products, 
cereals, flour, meal, etc. may be at- 
tacked temporarily by the mites, 

causing severe itching and irritation of the skin, known as 
itch." 

Tyroglyphus siro Linn, is the cheese mite, also found in grain and 
stored products ; T. farince De G. (Fig. 213) is known as the flour mite 
but is probably the same as the former. 




Fig. 213. — A stored food mite or flour 
mite, Aleurobius (Tyroglyphus) farince 
(male). X 145. 



grocer s 



1 Goldberger, J., and Schamberg, J. F., 1909. Epidemic of an articariod 
dermatitis due to a small mite (Pediculoides ventricosus) in the straw of mat- 
tresses. U. S. Public Health Reports, Vol. 24, No. 28, pp. 973-975. 

2 Webster, F. M., 1910. A predaceous mite proves noxious to man. 
U. S. Dept of Agr. Bu. of Ento. Circ. No. 118, 24 pp. 



350 MEDICAL AND VETERINARY ENTOMOLOGY 

No doubt the best way to destroy mites occurring in stored products 
is to subject them to a dry heat of 125° F., or by fumigation with sulphur 
or carbon dioxide. 

H. Red Spiders 
Family Tetranychidce 

Characteristics of Tetranychidae. — To this family belong the "web- 
spinning mites/' most commonly infesting vegetation and destructive 
to fruit trees and other plants. The term "red spiders" is ordinarily 
applied to the group. Tetranychus bimaculatus Harvey attacks many 
species of plants and is very injurious to hops. 

Persons employed in picking hops and harvesting almonds, etc., 
often complain of itching produced by the red spiders, but this soon 
disappears. 



CHAPTER XX 
VENOMOUS INSECTS AND ARACHNIDS 

Insect Venoms. — Insect venoms, like other animal venoms, are 
toxic principles probably not greatly unlike the bacterial toxins, but 
about which we know comparatively little. Unlike the bacterial toxins 
which reach injurious amounts after a period of incubation subsequent 
to the introduction of the corresponding bacteria into the body, the 
venoms on the contrary act almost instantly, i.e. as soon as introduced. 

The venoms act in one or more ways when introduced into the body, 
1st, they may act directly as solvents on the blood corpuscles (hcemo- 
lytic) ; 2d, they may act directly on the nervous system producing a 
shock or inhibiting reflexes {neurotoxic) ; 3d, producing an infiltration 
and congestion of blood {hemorrhagic) often in the vicinity of the wound 
or deeper tissue, such as the mesenteries, etc. A given specific venom 
may produce one or more of the above conditions. 

As has been discovered by various investigators and as is a matter of 
common observation, repeated inoculation of minute or attenuated 
quantities of a venom may lead to immunity, so also with venoms or 
poisons of bees, bedbugs, mosquitoes, fleas, cone-noses, etc. 

In the ants, bees and wasps (aculeate hymenoptera) there are 
two poison-secreting glands, one of which produces formic acid and the 
other an alkaline fluid. The combination of the two agents in certain 
proportions is evidently necessary to produce the reaction of a bee sting. 

The scorpion (an Arachnid) secretes a large quantity of colorless 
acid-reacting liquid soluble in water and heavier than the same. Ac- 
cording to Calmette, less than 0.0005 gm. will kill a white mouse in about 
two hours. 

How the Venom is Introduced. — Venoms of insects in a broad sense 
are introduced into the bodies of animals in one of three ways : 1st, by 
contact, e.g. irritating hairs of certain caterpillars, such as the brown-tail 
moth {Euyroctis chrysorrhaa Linn.), producing a condition similar to 
nettling, or the vesicating fluids of the blister beetles (Meloidse), par- 
ticularly Lytta wsicatoria Linn. ; 2d, by the bite or thrust of a piercing 
proboscis, as in the cone-noses (Reduviidse), or pierce of the chelicerse 
of spiders ; 3d, by the sting, as in the bees or wasps (aculeate Hymen- 
optera) and the scorpion. The operation and structure of stings varies 
considerably, notably in the examples cited. 

Irritating or Nettling Hairs. — A rash known as the " brown-tail 
rash " is traceable to the caterpillar of the brown-tail moth (Euproctis 

351 



352 MEDICAL AND VETERINARY ENTOMOLOGY 

chrysorrhcea Linn.), a common and very destructive shade tree pest in 
Europe and in America, especially New England. When the cater- 
pillars of this species molt, myriads of tiny barbed hairs are shed with 
the skin. When dry these hairs are blown about by the wind and 
coming in contact with the skin of the face or hands produce a very 
severe dermatitis. The hairs are hollow and it has been shown by Tyzzer 
that they contain a definite poisonous principle which is injected into 
the circulation by the sharp-pointed hair in contact with the skin, thus 
producing the rash. 

Blister Beetles. — Blister beetles belong to the family Meloidse 
(= Cantharidse) (Order Coleoptera) and are so designated because of 
their vesicating properties, i.e. the application of the pulverized bodies of 
many species, if not all, produces a blistering of the skin. The most 
notable example of the Meloidse is the Spanish fly, Lytta vesicatoria 
Linn, (see Chap. VI). 

The Meloidse (= Cantharidse) are described by Comstock, viz., 
" The blister beetles are of medium or large size. The body is compara- 
tively soft ; the head is broad, vertical and abruptly narrowed into a 
neck ; the prothorax is narrower than the wing covers, which are soft 
and flexible ; the legs are long and slender ; the hind tarsi are four- 
jointed, and the fore and middle tarsi are five- jointed." 

The blister beetles deposit their eggs on the ground, the larvae are 
active and feed it is said in some species on the eggs of locusts and soli- 
tary bees, others are predaceous. They undergo a number of changes 
not usual to insects and their development is consequently termed 
hypermetamorphosis. The adults are vegetable-feeding. 

Venomous Insects 

Cone-noses or Kissing Bugs, belonging to the Fam. Reduviidse (see 
Chap. VIII), are most commonly concerned with the more painful 
" bites " inflicted by insects. Their mouth parts (see Chap. IV) are 
beautifully adapted to piercing the skin or covering of the host. The 
Reduviids are essentially predaceous, attacking many species of insects, 
particularly plant lice and other soft-bodied forms from which they suck 
the body fluids. Attack upon humans is made principally, if not wholly, 
in self-defense. Persons picking up boards, sticks or stones, etc., may 
accidentally also pick up one of these insects, or in plucking a leaf or 
flower from a tree or other plant the fingers may close upon the insect 
as well, with the result that a very painful bite is almost invariably 
inflicted. 

The principal offenders are about 18-20 mm. in length and all bear 
a general resemblance to the illustration (Fig. 214). Among the impor- 
tant species in their relation to human comfort are the following : 
Opsicoetes (Reduvius) personatus Linn., known as the "kissing bug"; 
Conorhinus sanguisnga Lee, the " blood-sucking cone-nose " or " big bed- 



VENOMOUS INSECTS AND ARACHNIDS 



353 



bug " ; Conorhinus protractus Uhler, the " China bedbug " ; and Rasahus 
biguttatus Say, the "two-spotted corsair." 

The symptoms produced by Conorhinus protractus, the usual culprit 
in California, are described as follows : " In a few minutes after a bite 
the patient develops nausea, flushed face, 
palpitation of the heart, rapid breathing, 
rapid pulse, followed by profuse urticaria all 
over the body. The symptoms vary with in- 
dividuals in their intensity/' 

The symptoms described for Rasahus 
biguttatus are as follows : " Next day the in- 
jured part shows a local cellulitis with a 
central spot ; around this spot there fre- 
quently appears a bulbous vesicle about the 
size of a ten-cent piece and filled with a dark 
grumous fluid ; a smaller ulcer forms under- 
neath the vesicle, the necrotic area being 
generally limited to the central part, while the 
surrounding tissues are more or less swollen and somewhat painful." 

Treatment for Cone-nose Bites is discussed in a previous chapter 
(Chap. VIII). 

Bedbugs (Fam. Acanthiidse = Cimicidse), Fleas (order Siphonap- 
tera) and Mosquitoes (Fam. Culicidse), all inflict bites of greater or less 
severity, depending on individual cases. To many persons the bite of any 
one of the above proves benign, while to others even one bite may prove 
very irritating. Frequently the severity of a bite is traceable to an infec- 
tion induced by undue scratching with the finger nails. Ordinarily the 
itching may be relieved by the application of ammonia. For a discussion 
of each of the groups the reader is referred to the respective chapters 
dealing with the same. 




Fig. 214. — Atypical blood- 
sucking cone-nose, Cono- 
rhinus protractus. X 2. 



The Bee Sting — Structure and Operation 



The Bee Sting. — For precision exhibited in minute parts and for 
accuracy of operation, the sting of the honeybee {Apis mellifera Linn.) 
stands unsurpassed among the weapons of defense and offense carried 
by insects. From the barefoot boy that plays in the flower-dotted 
meadow, to the philosopher delving in the mysteries of a locust blossom 
at close hand, the sting of the bee demands instant respect. Cheshire 
has nicely stated the matter thus : "Man and bees alike live in a world 
where good and evil grow together, where the thrift of the industrious 
excite the cupidity of the idle. Let us then, accepting the sting with- 
out regret, strive to learn the way in which, for us, it shall cease to be an 
evil." 

The following account of the morphology and operation of the bee 
sting has been prepared by Miss Edwina Fay Frisbie and is an extract 



354 MEDICAL AND VETERINARY ENTOMOLOGY 



from a thesis oh this subject prepared under the direction of the 
writer. 

Morphology of Sting. — Accepting the sting as a specialized ovi- 
positor the worker bee, or aborted female, is used. The sting can be 
easily extracted either by separating the segments of the abdomen from 
it by means of dissecting needles, or by squeezing the live bee between 
forceps, which pressure causes it to protrude the sting. The sting can 

then be grasped with 
other forceps and 
drawn out. After ex- 
traction, the sting can 
be best examined 
when the parts are 
floated out in a few 
drops of glycerine. 
For purposes of de- 
scription the sting 
may be divided into 
three parts, viz. : the 
piercing apparatus ; 
the lateral plate and 
appendages ; the poi- 
son sac and glands. 

The piercing ap- 
paratus itself consists 
of three parts, one the 
so-called sheath, the 
other two lying within 
the sheath, and par- 
tially surrounded by 
it. In appearance the 
sheath is yellowish 
and translucent. The 
darts, which present 
concave surfaces to 
one another, are 
highly chitinous. The 
distal one third of the 
dart possesses a series 
of sharp barbs, whose shape has been aptly compared to the tip of a 
crochet needle. Cheshire states that each dart has from three to six 
barbs, other writers seem doubtful as to the number. The careful 
observations of the writer in which many barbs have been examined 
give no instance in which it was impossible to distinguish ten barbs 
on the outer edge of each dart (Fig. 215). Several writers state that 
poison pores are to be found at the base of each barb, from which 



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Fig. 215. — Sting of a honeybee (Apis mellifera). a, the 
two serrated darts ; b, b' ', sting palpi ; c, venom (poison) 
sac ; d, venom gland ; e, e', triangular plates or levers ; 
/, /', semilunar plates or levers; g, g', lateral plates or 
levers ; h, h', ^/-shaped darts ; i, i' , points of attachment 
for darts to levers ; e, e' ; j, j' , points around which levers 
rotate ; k, k', points of attachment for levers/, /'. X 17.5. 



VENOMOUS INSECTS AND ARACHNIDS 355 

poison exudes. In this matter, experience forces the writer to agree 
with Snodgrass in his remark that thus far he has failed to observe the 
exit of poison elsewhere than between the darts at their tip. 

Proceeding upward on the dart from the tiny barbs, the darts are 
seen to form a figure Y as they lie within the sheath. The arms of the 
Y gradually bend laterally. The plates attached to the upper edges 
of these laterally bent arms will be described under the next heading. 
One of the most remarkable portions of the darts is the poison valve 
with which each is provided. At the point of separation, the darts 
each present a delicate cup-shaped valve, whose closed portion is directed 
downward toward the tip of the sting. This is formed of the same 
chitinous material which composes the darts, and each is free to move 
with the movement of the dart. In order to accommodate this enlarge- 
ment of the darts, the sheath at this point expands to about five times 
its smallest diameter, which is at the tip of the sting. For at least one 
third of its length the sheath at this portion is expanded into a sym- 
metrical oblong body providing ample room for the movement of the 
darts and valves within. 

A curious structure, said by many writers to be found on the sheath, 
consists of two delicate, but strong, chitinous tracks or guide rails on 
which the darts, correspondingly grooved, fit and move back and forth. 
Since the sheath does not sufficiently surround the darts to direct their 
course, this guide-rail system which Carlet has observed, and which is 
accepted by other authors, offers a pretty and probable solution of the 
reason for the smooth and accurate play of the darts within the sheath. 

Lateral Appendages. — The lateral appendages are of three kinds, 
viz. : semilunar, triangular and lateral, according to shape or posi- 
tion. Both the semilunar and triangular plates are attached to the 
bent ends of the Y-shaped darts. The triangular plates are attached 
to the arms of the darts almost at their extremities, while the semilunar 
ones are connected for about one third of the distance from the ends 
of the arms. Permitting this comparison of the smallest of the plates 
to a triangle, although the comparison is not an exact one, the expla- 
nation of its position may be continued by saying that the apex of the 
triangle is that portion which is attached to the extremity of the dart. 
The other two points then point outward and downward, and serve as 
points of attachment for two elevated edges on the lateral plates which 
hang thus suspended. As they hang, half of their surface lies above 
and covers the dorsal surface of the semilunar plates just beneath them. 
Continuing in the same straight line with the semilunar plates and 
attached at their extremity to them, lie the fleshy palpi covered with 
delicate hairs. This outline description of the position and attachment 
of movable plates will be supplemented in the explanation of their mech- 
anism, where they can be more readily understood through their function. 

Venom Sac and Glands. — The third portion which completes the 
structure of the sting is the venom sac and glands. In order to under- 

2 a 



356 MEDICAL AND VETERINARY ENTOMOLOGY 

stand these, it is necessary to know that Hymenoptera are divided into 
those which kill their prey by stinging, and those which only paralyze 
them. The former are the most complicated for they possess two 
poison glands. One, the formic acid gland, which opens directly into 
the great poison sac, is the larger of the two. The other, the alkaline 
gland, which is comparatively small, is situated at the base of the 
poison sac. It is the combination of the formic acid and alkaline sub- 
stances from the two glands that results in the death of the attacked 
insect, or that causes the extreme irritation in humans. 

The formic acid gland alone is found in the Hymenoptera, which 
only paralyze their prey when stinging them. This fact has led various 
observers to make chemical tests of both the formic acid and alkaline 
substance. The result, according to Carlet and others has been to 
show that neither substance by itself is effective except to paralyze, 
but when combined the substances have deadly effects upon other in- 
sects. Carlet' s experiments to prove this were made upon house flies 
and blow flies by injecting each substance singly and then introducing 
both into the body of a fly. The results are entirely convincing. 

Operation of the Sting. — After considering the very complicated 
structure of this minute instrument of attack and defense it will not be 
surprising to find, perhaps, that the mechanism of its parts is even more 
complicated and at the same time so wonderfully accurate that human 
invention can only look and marvel. 

The microscopic structure of parts makes an examination of the 
mechanism extremely difficult. Also the stubbornness which charac- 
terizes a bee when it would be persuaded to sting without the usual 
incentive, adds to the problem of studying the operation of the sting. 
An effort was made to see the sting in operation by confining a bee on 
its dorsal side and then prodding it until its sting was angrily thrust 
in and out. This process showed three things, viz. : that the sharp- 
pointed sheath was always first to appear when the thrust was made; 
second, that the darts inside the sheath worked back and forth alter- 
nately, and quite independently of the sheath or of one another ; third, 
that the poison was exuded in droplets from the tip of the sting between 
the darts. Beyond these points, observation of the mechanism of the 
sting was impossible, but the description of Cheshire's observations 
gives a very clear and plausible explanation. 

" The sheath has three uses ; first, to open the wound ; second, to 
act as an intermediate conduit for the poison; and third, to hold in 
accurate position the long-barbed darts. The sheath does not inclose 
the darts as a scabbard, but is cleft down the side which is below, when 
the sting points backward. The darts, as soon as their ugly barbs 
establish a hold, first one and then another drive back and forth by suc- 
cessive blows. These in turn are followed by the sheath, when the 
darts again plunge more deeply, until the murderous little tool is buried 
to the hilt. But these movements are the result of a muscular appara- 



VENOMOUS INSECTS AND ARACHNIDS 357 

tus yet to be examined. The dovetail guide-rails of the sheath are 
continued far above its bulbous portion, and along with these the darts 
are also prolonged upward, still held to the guides by the grooved 
arrangement; but both guides and darts, in the upper part of their 
length, curve from each other like the arms of the Y, before mentioned, 
to points C, C (Fig. 215) where the darts make attachment to two 
levers (i, i'). The levers, or plates, as they are called (Kl and K'l"), are 
provided with broad muscles, which terminate by attachment to the 
lower segments of the abdomen. These, by contraction, revolve the 
levers aforesaid round the points /, /', so that without relative move- 
ment of rod and groove, the points c, c' approach each other. The 
arms of the Y straighten and shorten, so that the sheath and darts are 
driven from their hiding place together and the thrust is made by which 
the sheath produces its incision and fixture. The sides being sym- 
metrical, we may, for simplicity's sake, concentrate our attention on 
one, say the left in the figure. A muscular contraction of a broad strap 
joining K and D (the dart protractor) now revolves k on I, so that a 
is raised, by which clearly c is made to approach d ; that is, the dart is 
sent forward, so that the barbs extend beyond the sheath and deepen 
the puncture. The other dart, and then the sheath, follow, in a se- 
quence already explained, and which G is intended to make intelligible, 
representing the entrance of the sheath, b the advance of the barbs, 
and c the sheath in its second position. The barb retractor muscle is 
attached to the outer side of i, and by it a is depressed and the barbs 
lifted. These movements, following one another with remarkable 
rapidity, are entirely reflex, and may be continued long after the sting 
has been torn, as is usual, from the insect. By taking a bee under the 
microscope and forcing the sting into action, the sting movement will 
be seen to be kept up by continued impulses from the fifth abdominal 
ganglion and its multitudinous nerves, which penetrate every part of the 
sting mechanism and may be traced even into the darts. These facts 
will show why an abdomen separated many hours may be able to sting 
severely, as I have more than once experienced." 

Sting in Situ. — It can readily be seen that the sting originates from 
the seventh and eighth segments and lies between the oviduct and the 
rectum above. The darts of the sting follow the ventral line of the ab- 
domen and are held in place by the sheath situated just above, while 
the barbs of the darts are pointing downward and outward. In a space 
above the sheath lie the fleshy palpi. The delicate attachment between 
the sting and the organs of the abdomen is here indicated, for only a 
small portion of the sting, in comparison with its size, has any connection 
with parts in the abdomen. This accounts for the ease with which the 
sting is torn from the abdomen when the barbs become imbedded after 
a thrust of the darts is made. 

Stinging Insects. — The stinging insects belong to the order Hy- 
menoptera, suborder Aculeata, and are best known as the ants, bees, 



358 MEDICAL AND VETERINARY ENTOMOLOGY 



and wasps, in which the females of all species are provided with a spe- 
cialized ovipositor known as a sting, more or less well developed for 
piercing the skin of higher animals or other insects. The sting is used 
either as an organ of defense or offense, in the latter case often to procure 
food for the young. 

The principal aculeate Hymenoptera are divided into the following 
superfamilies : viz. : Formicina, the true ants ; Sphecina, the digger 
wasps ; Vespina, the true wasps ; and Apina, the bees. 

The superfamily Formicina includes the true ants, which are divided 
into three or more families, Formicidse, Poneridse, and Myrmicidse. 
One of the most formidable stinging ants in California is Pogonomyrmex 
calif ornicus Buck. This ant will not only attack humans but also smaller 
domesticated animals. Thus hog raisers in the Imperial Valley, Cali- 
fornia, report many pigs killed by ants, one farmer reporting a loss of 400 
small pigs during one year and another 100 to 150 during a period of three 
years, — all killed by ants. 

Ants of this species are very abundant in the Imperial Valley, and it 
is a matter of common observation to see a small pig walk leisurely upon 

an ant mound and suddenly begin to kick 
and squeal, due to the terrific attack of 
the myriads of ants rushing forth from 
the nest. The writer has meager experi- 
mental evidence to deny the popular opin- 
ion above stated. The pig is certainly 
very uncomfortable during the attack, but 
experimental evidence of paralysis and 
death due to the ants has not been se- 
cured. However, much more work needs 
to be done to safely deny the statements 
of practical hog raisers. 

The ants may be destroyed by apply- 
ing kerosene to the nests, using a funnel 
or hollow rod to reach the deeper parts; 
potassium cyanide in liquid form may also 
be used, but great care must be exercised 
both in the preparation and application 
of the same owing to its very poisonous 
nature. 

Among the Vespina, the best-known stinging species belong to the 
family Mutillidse, the velvet ants, also known as the woolly ants, cow 
killers, etc. (Fig. 216). The velvet ants are covered with hair and 
the body is commonly banded with two or more strongly contrasting 
colors. There are very many species of Mutillids, most of which 
measure from \ to 1 inch in length. A very common species in the 
central states of the United States is Splicer ophthalmia occidentalis 
Linn., a black species with a scarlet band. This species is very com- 




Fig. 216. — A velvet ant (Mutilla), 
also known as a "cow killer." 
X2.2. 



VENOMOUS INSECTS AND ARACHNIDS 



359 



mon on the beach sands of Lake Erie, causing bare-foot bathers much 
distress. 

Many of our large dusty yellow to cinnamon colored species belong 
to the genus Mutilla and are commonly called " cow killers " (Fig. 216). 
These occur abundantly among dry leaves along the roadside or by- 
paths in the woods. 

To the Vespina also belong the yellow jackets or hornets, Vespa 
maculata Linn., and other species which build large nests in the branches 
of trees, also the mud daubers Pelopceus cementarius Drury, Polistes 
pallipes Lep., and Polybia flavitarsis Sauss., et ah These species with 
their relatives belong 
to the family Vespidse, 
and all have a well- 
developed sting which 
may be used on the 
least provocation. 

Of the solitary 
wasps belonging to the 
superfamily Sphecina, 
the great digger wasp 
or " cicada killer," 
Sphecius speciosus Say 
(Fig. 217), is the most 
formidable. This spe- 
cies, a member of the 
family Bembecidse, is 
nearly an inch and a 




Fig. 21' 



A digger wasp (Sphecius speciosus). X 1.1. 



half in length, is black with yellow segmentally arranged partial bands 
on the abdomen. This wasp easily brings to earth very large cicadas, 
carries its prey to a previously prepared burrow where eggs are de- 
posited and the larva? develop in the cicada. 

Underground wasps' or hornets' nests may be treated successfully 
with carbon bisulphide, while sulphur fumigation or thorough spraying 
with kerosene will suffice to destroy the nests of wasps built in the 
branches of the trees. Night treatment is suggested. 

The true bees belong to the superfamily Apina, the honeybee Apis 
mellifera Linn., a member of the family Apidse, and the bumblebee 
Bombus fervidus Fabr. and others belonging to the family Bombidse. 



Spiders 
Class Arachnida — Order Araneida 

Characteristics of the Araneida. — All spiders belong to the order 
Araneida in which the abdomen is sac-like and unsegmented, joined to 
the cephalothorax by a slender pedicel. According to Comstock 1 



Co. 



Comstock, John 
xv + 731 pp. 



Henry, 1912. The Spider Book. Doubleday, Page & 



360 MEDICAL AND VETERINARY ENTOMOLOGY 

the chelicerse are usually claw-like, " folded back into a groove in the 
basal segment, like the blade of a pocketknife into a handle," i.e. uncate ; 
or they may be pincer-like {chelate), " there being a prolongation of the 
first segment which is opposed to the claw." The pedipalps are more or 
less leg-like. The four pairs of legs are all fitted for walking. There are 
usually present eight eyes but these may be reduced to six, four, two or 
none. The respiratory organs of spiders are either book lungs or trachea?, 
or in most species a combination of the two. The book lungs are sacs 
which open on the ventral side of the abdomen by means of slit-like spir- 
acles. Within each sac there is a series of lamellate folds. The tracheae 
are far less developed than in insects and are much more localized. 

The Araneida are divided into more than thirty families. 

Spider Venoms. — All spiders secrete venom by means of which they 
kill their prey. The venom glands are located in the anterior portions of 
the cephalothorax and are two in number. " Each gland discharges 
its product through a long slender duct which opens near the tip of the 
claw of the chelicera of the corresponding side of the body. This open- 
ing is so placed that it is not closed by the pressure of the bite, but allows 
the venom to flow into the wound. In the tarantulas each gland is situ- 
ated in the basal segment of a chelicera. The glands are sac-like in form ; 
the lumen of the sac serves as a reservoir of venom ; the wall is composed 
of excreting cells, supported by a layer of connective tissue, and there is 
a layer of muscle fibers surrounding the sac " (Comstock). 

While spider venom is very destructive to the life of insects upon 
which spiders prey, there is little evidence (with certain exceptions) 
to indicate that this venom is injurious to man. Most of our so-called 
spider bites are traceable to other sources, particularly cone-noses 
(Reduviidse). Comstock (1912, loc. tit.) has given much attention to 
this matter and has come to the conclusion that there are no spiders 
that need be feared in the northern part of the United States at least, 
and in the South there is only one dangerous genus, Latrodectes. As 
to the so-called tarantula (Heteropoda) which is brought to the North 
in bunches of bananas Comstock has the following to say : " This, how- 
ever, although a large spider is an inoffensive one. Mr. John T. Lloyd 
informs me that he has collected scores of specimens of this species with 
his hands in Samoa, where it is abundant, and has never been bitten by 
it." 

The Hourglass Spider (Latrodectes mactans Fabr.), also known as 
the " black widow " or " shoe button" spider, is a medium-sized, glossy 
black, naked spider. The females measure from one to one and a 
fourth inches in length over all, while the males are less than an inch in 
length. The abdomen is globose, marked ventrally with brick-red 
triangular spots (Fig. 218). These spots vary in arrangement, — often 
two of these touch base to apex, or apex to apex, not unlike an 
hourglass in outline, or there may be four, roughly arranged like a Mal- 
tese cross ; in some individuals only one spot may be seen. The males 



VENOMOUS INSECTS AND ARACHNIDS 



361 



and immature females are variously striped and spotted with lighter 
markings. The species belongs to the family Theridiidse. 

Latrodectes mactans occurs quit ecommonly in California and the 
South, also the West Indies, Madagascar, New Zealand and Algeria, 




Fig. 218. — A venomous spider, Latrodectes mactans 



and has the reputation of being extremely venomous. Sundry speci- 
mens have been sent to the writer at various times, and occasional re- 
ports of its having caused dangerous and even fatal illness in California 
have been made, but unfortunately very little experimental evidence 
seems to be available. 

An account of a fatal case in North Carolina is given by Packard and 
Howard, 1 viz. : An employee (farm laborer engaged in hauling wood) 
of Mr. John M. Dick is reported to have been bitten by a black spider 

1 Packard, A. S., and Howard, L. 0., 1899. A contribution to the literature 
of fatal spider bites. Insect Life, Vol. 1, No. 7, pp. 204-211. 



332 MEDICAL AND VETERINARY ENTOMOLOGY 

with a red spot on it at about 8.30 o'clock a.m., dying of the effects 
about fourteen hours later, i.e. between 10 and 11 o'clock p.m. The 
victim is said to have felt something crawling on his neck, and as he 
brushed it off it bit him very severely, causing very great pain. The 
cause was described as being a black spider with red spots. An examina- 
tion of the neck revealed ten little white pimples, all of which could be 
covered with a one-dollar silver coin; no puncture was seen. There 
was no swelling, but the neck, left breast and arm were so hard that no 
impression could be made with the thumb. The man complained of 
pain running through his entire body. It should be noted that the man 
was perfectly healthy. By one o'clock the pain had settled in his bowels 
and shortly thereafter he was attacked with spasms. About four o'clock 
spasms recurred and the patient lapsed into unconsciousness and re- 
mained so until death. 

In the same paper the authors refer to the investigation of Dr. Graells, 
appointed by the Academy of Medicine and Surgery at Barcelona in 
1833 to investigate the reported venomous nature of the " Malmignatte " 
of southern Europe (Latrodedes malmigniatus Walck). Graells re- 
ported the following symptoms : 

"A double puncture surrounded by two red circles, which unite, together 
forming an edematous areole which marks the seat of a tumor which develops 
later. The pain extends and soon occupies the length of the bitten limb, and 
often reaches the axillary or inguinal glands, according to the limb bitten. 
These glands tumefy and become painful and the skin between them and the 
bite becomes marked with livid spots which seem to follow the course of the 
lymphatic vessels. The pain continues, reaching the body even to the ab- 
dominal and thoracic cavities, with a sensation of burning heat, strong con- 
striction or soreness of throat, tension of the abdomen, tenesmus, and extreme 
headache, which makes itself felt along the spinal column ; soon followed by 
general convulsions, more particularly in the extremities, followed by insensi- 
bility, especially in the feet, which are ordinarily livid, while the whole body is 
swollen. This imposing array of symptoms brings about a very marked low 
spirit on the part of the patients, indicated by their expressions of despair, of 
profound affliction, or fear concerning the return of the health, for they be- 
lieve themselves threatened with approaching death. 

"They continually change from place to place in their bed, giving utterance 
to sighs and plaintive cries, carrying their hands to their heads mechanically, 
or they say that they feel their brain pricked by pins. The face is sometimes 
red and burning or others pale. The difficulty of respiration is marked, the 
pulse is very low, quick, irregular, the skin cold and rather moist from an abun- 
dant cold and viscid perspiration; at the same time the patient complains 
that his bowels are burning and asks for fresh water. In some cases the sight 
is almost totally obscured, and conjunctiva injected ; in others the voice becomes 
weakened, and perhaps a ringing in the ears becomes very marked. Sometimes 
livid spots appear over the whole body. The intensity of these symptoms varies 
according to the susceptibility of the individual, to the strength of the Latro- 
dedes, and also the number of bites which the patient has received. 

"Recovery comes sooner or later according to the strength of the patient, 
the energA^ of the remedies, and the promptness of their effect. In all cases it is 
announced by the perspiration, which from cold and viscid becomes warm and 
vaporous ; by the quickening and regularity of the pulse ; by increasing facility 



VENOMOUS INSECTS AND ARACHNIDS 



363 



in respiration and urination ; by the cessation of the inflammation of the glands 
and of the aching in the brain and spinal cord, which passes into a sort of lethargy 
which may be more the effect of the laudanum given than a symptom of the 
disease." 

In many respects the above symptoms apply to the two cases reported 
to the wTiter by the late Mr. Charles Fuchs, Curator of Insects, Cali- 
fornia Academy of Science ; however, the local effects in these two cases 
were very much more severe. 

According to Comstock (1912, he. cit), Merriam (1910) in " The 
Daion of the World, Myths and Weird Tales told by the Mewan Indians of 
California" the Northern Mewuk says : " Po'ho-noo the small black spider 
with a red spot under his belly is poison. Sometimes he scratches people 
with his long fingers, and the scratch makes a bad sore. . . . All the 
tribes know that the spider is poisonous and some of them make use of 
the poison." The latter states also that the California Indians rank 
this spider with the rattlesnake as poison, and mash the spider to rub 
the points of their arrows in it. 

Habits and Life History of Latrodectes mactans. — This spider 
occurs, when in its geographical range, not uncommonly in old out- 
buildings, old barns, stables, woodpiles, etc. It spins a rough web in 
which it catches its prey, mainly flies 
and other insects. It is an exceed- 
ingly aggressive species, as the writer 
has observed in the several grown 
individuals under observation at 
various times in the laboratory. The 
egg cocoons (Fig. 219) are spun dur- 
ing the summer, and are well pro- 
tected by the web and carefully 
guarded by the female. Each egg 
cocoon contains three hundred, more 
or less, rather large eggs. The in- 
cubation period in observed cases at 
a maintained temperature of 27 ± 
1° C. was about thirty days, — for 
example a spider spun her egg cocoon 
during the night of July 17, the eggs hatching during the night of 
Aug. 13. Seven egg cocoons were spun by one spider, but the eggs 
contained in the seventh did not hatch. 

The young spiders (Fig. 220) are gray, quite unlike the adult in this 
respect, and are very active, attacking plant lice, etc. at once. The first 
molt takes place within a week, followed by numerous molts at intervals 
of a week or more. The young spiders grow darker with each molt, 
with the appearance, however, of creamy white lines or spots dorsally on 
the abdomen. The reddish ventral markings appear within a month 
ordinarily. Growth is very rapid during the rest of the summer and 




Fig. 



'10. 



Egg cocoon of Latrodectes 
mactans. X 2. 




364 MEDICAL AND VETERINARY ENTOMOLOGY 

autumn, but maturity is not reached until the following spring or early 
summer. 

Tarantulas. — The term tarantula is applied to the very large spiders 
belonging to the Family Aviculariidse occurring in California and other 
tropical and subtropical climates. The best-known species in California 
is Eurypelma (Mygale) hentzii Girard, also known as a bird spider, as 

is Avicularia californica Banks. 
While these spiders are much 
dreaded there is little or no evi- 
dence to warrant this fear. The 
common trapdoor spider of Cali- 
fornia is Bothriocyrtum californi- 
cum Cambridge, also greatly 
feared by many persons. 

The term tarantula was first 
applied to an European species, 

Fig. 220. — Young stages of Latrodectes mac- ly C0Sa tarentuld, which according 
tans. Left, ventral view, showing reddish a ~ , , ' , , 

hourglass-like marking on abdomen ; right, to ComstOCK does not belong to 

dark^Sg^°TI wMte abdomen ™ th the spiders to which this term is 

applied in America. 

To the bite of Lycosa tarentula is referred the hysterical disease known 
as tarantism said to have been common in southern Europe in the 
Middle Ages. 

The following account of tarantism is taken from the Cambridge 
Natural History, Vol. IV, p. 361 : " The bite of the spider was supposed 
to induce a species of madness which found its expression — and its cure 
— in frantic and extravagant contortions of the body. If the dance 
was not sufficiently frenzied, death ensued. In the case of survivors, 
the symptoms were said to recur on the anniversary of the bite. Particu- 
lar descriptions of music were supposed to incite the patient to the ex- 
cessive exertion necessary for his relief ; hence the name ' Tarantella.' 

" In the middle ages epidemics of ' tarantism ' were of frequent oc- 
currence and spread with alarming rapidity. They were seizures of an 
hysterical character, analogous to the ancient Bacchic dances, and quite 
unconnected with the venom of the spider from which they took their 
name. The condition of exaltation and frenzy was contagious, and 
would run through whole districts, with its subsequent relapse to a state 
of utter prostration and exhaustion. The evil reputation of the Taran- 
tula appears to have exceedingly little basis in fact." 

Venomous Ticks 

Class Arachnida, Order Acarina 

Ticks producing local or systemic disturbances by their bite alone 
are known in both families, Ixodidse and Argasidse (see Chap. XVIII), 
though more commonly in the latter. 



VENOMOUS INSECTS AND ARACHNIDS 365 

Ordinarily little or no injury results from the mere bite of an Ixodine 
tick, — the writer has known of Dermacentor occidentalis Neumann and 
Dermacentor variabilis Say to remain'attached to a person for days without 
causing great inconvenience and occasionally quite unobserved by the 
host. However, Nuttall (1911, loc. cit., p. 133) records a number of cases 
cited by other authors in which the bite of Ixodes ricinus Linn, has caused 
serious consequences, notably a case described by Johannessen of a " boy 
where the tick's body was removed but the capitulum remained em- 
bedded in the skin at the back of the head. Swelling followed at the 
point of injury, accompanied by headache, stiffening and cramps in the 
muscles of one side, partial loss of memory and polyuria ; the pupils 
became dilated, etc. The boy made a slow recovery." Blanchard is 
quoted by the same author as stating " that accidents of a grave char- 
acter occasionally follow ricinus bites, the wound serving as a center from 
which infection may spread to the rest of the body." 

Quite a number of species included in the Family Argasidse are 
known to cause more or less serious consequences by their bites, notably 
Ornithodorus moubata Murray, 0. coriaceus Koch, and Argas persicus 
Neumann. 

Ornithodorus moubata Murray (see Chapter XVIII) has been re- 
ported repeatedly as causing marked consequences by its bite. Well- 
man as quoted by Nuttall (1908, loc. cit., p. 98) " states that the bite 
is very painful, the swelling and irritation (especially in Europeans) 
not subsiding for days. The wheals are hard, raised and swell most 
disagreeably if scratched, and this even a week after being bitten. The 
bite of young ticks (nymphse) is said by the natives to be more severe 
than that of the adults." 

Ornithodorus coriaceus Koch. — The attention of the writer has 
been repeatedly called to a very venomous species of tick commonly 
known as the " Pajaroello bug " occurring in isolated sections of Califor- 
nia and Mexico. Reports invariably indicate that the bite of a single 
individual produces very severe and often grave results. In conversa- 
tion with natives it was learned that this creature was more feared than 
the rattlesnake. Many harrowing tales are told regarding the loss of 
an arm or leg or even death due to the bite of this tick. No doubt 
much of this is greatly exaggerated ; however, the infected bite might 
easily lead to grave consequences. Mr. W. L. Chandler, a graduate 
student in the University of California, has given the writer an accurate 
account of two bites which he suffered while stationed in the San Antone 
Valley (California). The first bite was received July 2, 1912. He 
experienced a sharp pain on the left arm and upon rolling up his sleeve 
discovered a large tick, partly engorged, attached to the upper arm in 
front. He dislodged the tick and sucked the lesion. The lesion when 
first discovered showed a small dark purple ring surrounding a bright 
red spot, the point of attachment. The discoloration disappeared in a 
short time, but the arm was " highly irritable for two or three days and 



366 MEDICAL AND VETERINARY ENTOMOLOGY 

at the point of attachment a minute clear scab formed." The tick 
proved to be a " pajaroello. " 

The second bite took place July 16 while seated in a thicket of 
willows (the first bite took place while riding over a brush-grown hill), 
and in this case the sharp pain involved the left leg. An almost fully 
engorged tick (again a pajaroello measuring about f of an inch in length 
and about \ inch in width was removed from just above the shin. Once 
more a bright red spot was visible at the point of attachment, surrounded 
by an irregular purple ring about three-fourths of an inch in diameter. 
In about an hour the leg began to swell in the vicinity of the lesion, and 
in about three hours the entire lower leg was tremendously swollen. 
The coloration about the point of attachment had widened considerably, 
was puffy and a clear lymph exuded freely from the lesion. The young 
man lanced the leg, causing the blood to flow freely, and treated the wound 
with crystals of potassium permanganate, binding the leg with cotton 
and gauze. During the following night he reports experiencing a 
general disagreeable feeling, the entire lower leg "irritable and numb." 
On the following day the bite on the arm became irritable again, and was 
treated as had been the leg, fearing bad results. For several weeks 
both lesions exuded a clear lymph from beneath an "oily-looking, trans- 
parent, red mottled scab " which remained in evidence for two or three 
months. 

Chandler reported these ticks very numerous in some localities, having 
counted as high as six within half an hour crawling over a saddle blanket 
placed on the ground. Their presence and number seemed to be de- 
termined by the presence of cattle, although ticks were found where 
there were no cattle but in places which were evidently favorite haunts 
of large wild animals. 

Experiments with the Pajaroello. — A number of specimens of 
Ornithodorus coriaceus were collected in the San Antone Valley and at 
Newman, California, for purposes of experimentation and study of life 
history. In cooperation with Dr. W. A. Sawyer and Messrs. S. W. 
Newman and W. L. Chandler, the writer conducted a number of experi- 
ments particularly with reference to the bite. In one of these experi- 
ments a mature female tick (Ornithodorus coriaceus) was permitted to 
bite a nearly full-grown monkey (Macacus rhesus) twice with an interval 
of sixteen days intervening between the two bites. The tick was ap- 
plied at 9 : 42 a.m. Dec. 10, 1913 and began sucking blood at 9 : 43, 
one minute later, becoming engorged and falling off at 10 : 21 a.m., a 
period of 38 minutes. At 10 : 30 a few minutes after the tick dropped off 
there appeared a deep red hemorrhagic area 2 mm. in diameter at the 
point of biting with a somewhat lighter area 10 mm. in diameter sur- 
rounding the central area. At 10 : 27 there was a black spot at the point 
of bite 1.5 mm. in diameter, the inner red hemorrhagic area measuring 
4 mm., with a yellowish white area surrounding this 8X6 mm., and an 
outer red petechial area 15 X 13 mm. No general symptoms were 



VENOMOUS INSECTS AND ARACHNIDS 



367 



noted. As shown in Fig. 221 the lesion reached its greatest expanse 
the following day when the following measurements were taken : — 
dark purple spot 2 mm. in diameter (a very dark red scab) ; the inner 
red area 6X5 mm., the yellowish white area 20 X 12 mm., the outer 
area 48 X 23 mm. and fading. The yellowish white area including 
bite was slightly swollen. By Dec. 14, i.e. four days after the bite was 
received, the ecchymosis had entirely disappeared ; by Dec. 16, six days 




Fig. 221. — Showing venomous tick (Ornithodorus coriaceus) and lesion produced by same 
on skin of a monkey. (1) tick on skin before attaching; (2) tick attached and fully 
engorged ; lesion appears as dark shadow at anterior end of tick ; (3) shows lesion 
within a few minutes after tick has dropped off ; (4) lesion at expiration of five hours ; 
(5) lesion at expiration of twenty-four hours. (For description and extent of areas see 
text.) X .7. 



after the bite, the lesion was entirely gone but for a slight pigmentation, 
a thickened reddish area measuring 5X3 mm. and a small scab 2 mm. 
in diameter. 

The monkey remained normal throughout the experiment as regards 
temperature, weight, blood count and general condition. 

The second bite was received by the same animal on Dec. 26, the 
tick being applied at 9 : 43 a.m., taking hold at 9 : 44 a.m., and dropping 
off fully engorged at 9: 55 a.m., requiring but 11 minutes to engorge. 
The history of the second bite follows that of the first very closely, ex- 



368 MEDICAL AND VETERINARY ENTOMOLOGY 

cept for the extent of the lesion, which was greater, i.e. 70 X 31 mm. In 
order to note any manifestations on the part of the first lesion, the second 
bite was located near the opposite nipple. No change was observed. 



ti&^?C*$* 



' '!£*'fi 



/ ♦ i ' 



' < > 






m^ ' 



§ * r %i., fe 






* *■ 



Fig. 222. — Showing Ornithodorus coriaceus just backing away from her eggs recently de- 
posited in the sand. Note the protective coloration of the tick. X 5. 

The lesion produced by the second bite had disappeared by December 
31, i.e. five days after the bite, except for a slight thickening 3 mm. in 
diameter and a slight white scale at the center. Again the monkey had 



I 



VENOMOUS INSECTS AND ARACHNIDS 369 

remained normal, except for a slight increase in the count of white blood 
corpuscles, which rose from 7400 at the time of the bite to 13,900 by 
noon of the same day, going down again to 7300 by 5 p.m. 

Life History of Ornithodorus coriaceus. — The pajaroello deposits 
large plum-colored spherical eggs (Fig. 222). In the laboratory these 
are deposited on the sand in slight depressions. There are commonly 
four to seven layings at intervals of from several days to several weeks 
during the months of May to July, inclusive (as early as February under 
laboratory conditions), and the female is. known to deposit eggs for at 
least two successive seasons. The number of eggs observed per laying 
has been 61 to 323, with a total of from 747 to 1158 for one season. The 
incubation period at a maintained temperature of from 24° to 26° C. is 
from 19 to 29 days, with an average of about 22 days. 

The larvae (Fig. 223) are very active, scattering quickly and attach- 
ing readily to a host, particularly rabbits. Experimentally the human 
has also served as a 
larval host. The ear 
of a rabbit apparently 
affords a most satis- 
factory point for at- 
tachment. The larva 
remains attached to 
the host for a period 
of about seven days, 
becoming quite globu- 
lar and much enlarged. ^P 

Under favorable 
conditions the tick 
becomes sexually dif- 
ferentiated after the 
fourth molt, requiring 
about four months to 
reach this stage. Others 
have not become sex- 
ually differentiated Fig. 223. — Showing egg of Ornithodorus coriaceus and 
•j-k five -m^lfc Orrli larvae of the same in the act of emerging ; also two fullv 

Wltnn\e mORS. Ural- emerged individuals. X 14. 

narily the tick molts 

once for each engorgement, but there may be two molts between 

feedings. 

Even though sexual differentiation is accomplished during the course 
of one summer, there seems to be little evidence at present that there 
is more than one generation per year. 

Fully developed adult ticks were brought into the laboratory 
September 21, 1913, having been in captivity in the same stage four 
months previous and were still active and eager to bite January 1, 
1915, a period of about 20 months. No molts had taken place 




# 




370 MEDICAL AND VETERINARY ENTOMOLOGY 



during this time, notwithstanding the fact that full engorgement had 
occurred repeatedly and many eggs had been deposited. 

Remedies for Tick Bites. — For the bite of Ornithodorus moubata, 
Wellman (in Ms. according to Nuttall, 1908) " recommends prolonged 
bathing in very hot water, followed by the application of a strong 
solution of bicarbonate of soda, which is allowed to dry upon the skin. 
He states that this treatment is comforting. For severe itching he 
advises smearing the bites with vaseline which is slightly impregnated 
with camphor or menthol. Medical aid should be sought when compli- 
cations arise. " 

Scorpions 
Class Arachnida, Order Scorpionida 

Characteristics of the Scorpionida. — The most striking characteris- 
tics of the scorpions are, first, the formidable pedipalps terminating in 
strong lobster-like chelae ; second, the long tail-like postabdomen termi- 
nating in a bulbous sac and sting 
(Fig. 224). " The cephalothorax 
is compact and unsegmented ; the 
abdomen is broadly joined to the 
thorax . . . consists of seven seg- 
ments, and a slenderer tail-like divi- 
sion, the postabdomen or cauda, 
consisting of five segments. . . . 
The cephalothorax bears a pair of 
eyes near the middle line, the median 
eyes, and on each side near the 
cephalolateral margin a group of 
from two to five, the lateral eyes. 
A few scorpions are blind. . . . 
Scorpions breathe by means of 
book-lungs, of which there are four 
pairs, opening on the lower side on 
the third to the sixth abdominal 
segments. ... The sexes of scor- 
pions differ in that the male has 
broader pincers and a longer post- 
abdomen. Scorpions do not lay 
eggs, the young being developed 
within the mother; after the birth 
of the young, the mother carries 
them about with her for some time, 
attached by their pincers to all portions of her body. . . . Scorpions 
live in warm countries. They are common in the southern portion of 
the Ignited States, but are not found in the North. They are nocturnal, 




Fig. 224. — A scorpion, Hadrurus hirsutus. 
X .6. 



VENOMOUS INSECTS AND ARACHNIDS 371 

remaining concealed during the day, but leaving their hiding places at 
dusk. . . . They feed upon spiders and large insects, which they seize 
with the large chelae of the pedipalps and sting to death with their 
caudal poison sting" (Comstock). 

The order Scorpionida is divided into six families of which there 
are four in the United States, separated according to Comstock (1912, 
loc. cit.), viz. : 

A. Only one spur at the base of the last tarsal segment of the last pair of legs, 

and this is on the outside Scorpionidoe 

A A. One or two spurs on each side at the base of the last tarsal segment of the 
last pair of legs. 
B. From three to five lateral eyes on each side. 

C. Sternum triangular ; usually a spine under the sting Buthidoe 
CC. The lateral margins of the sternum nearly parallel; sternum 
usually broader than long; no spine under the sting 

Vejovidce 
BB. Only two lateral eyes on each side Chactidce 

Over three hundred species of scorpions are known, of which over 
sixty occur in the United States, of which the following are characteris- 
tic : 

Isometrus maculatus Linn., known as the spotted Isometrus, is 
widely distributed in tropical and sub-tropical countries. This species 
is described by Comstock as follows : "A dirty yellow species marbled 
and flecked with black. The body is thin and slender. In the female 
the postabdomen is usually about as long as the rest of the body ; in 
the male, it is often twice as long. The hand is long and thin, thinner 
than the tibia of the pedipalp ; the finger is from one and a half to two 
times as long as the hand. The combs x have from seventeen to nine- 
teen teeth. The female grows to nearly two inches in length ; the male 
to nearly three inches. 

Centrums carolinianus possesses a spine or tubercle under the sting ; 
body striped with black and yellow ; a small pale median spot on the 
anterior border of the cephalothorax ; legs pale yellow; postabdomen 
pale. Occurs in the Southern states (Comstock). 

Hadrurus hirsutus Wood is a very large and hairy species found in 
the Southeast. The penultimate tarsal segment of the first three pairs 
of legs is furnished with long hairs on the back (Comstock). 

Vejovis carolinus, a reddish brown species, occurs from South Carolina 
to Texas. 

Scorpion Sting. — The " aculeus" or sting of the scorpion is located 
terminally on the final bulbous segment. The bulbous segment in- 
closes a venom-containing vesicle connected with the sting which 
terminates in a hollow needle-like point. The sting curves downward 

1 The combs of a scorpion are located ventrally, originat ing from the 
"sclerite on the middle line of the body" just anterior to the first segment of 
the postabdomen. Each comb, of which there are two, is provided with so- 
called teeth. 
2b 



372 MEDICAL AND VETERINARY ENTOMOLOGY 



when the "tail" is extended, but upwards and forwards when the scor- 
pion poises for attack or defense, the entire tail-like postabdomen being 
curved dorsally and forwards. The victim is struck quickly and re- 
peatedly, the thrust being made quite 
near the head of the scorpion. 

Scorpion stings are quite common 
in California ; ordinarily most persons 
pay no more attention to the sting of 
a scorpion than to the sting of a wasp. 
The pain produced is instant and quite 
penetrating. In some instances the 
wound is quite severe and systemic 
disturbances may result. Fatal cases 
rarely if ever occur. 

Treating the wound promptly with 
ammonia ordinarily brings prompt 
relief. 



Whip Scorpions 
Class Arachnida, Order Pedipalpida 

Characteristics of Pedipalpida. — 

The Pedipalpida resemble scorpions 
in some respects in that the pedipalps 
are similar. The first pair of legs is 
elongated and tactile, while the last 
three pairs are ambulatory. The term 
"whip scorpion" is applied to the 
Family Thelyphonidse, because the ter- 
minal end of the abdomen is provided 
with a long slender many-segmented 
appendage (Fig. 225). "Grampus" 
and "vinegerone" are also common 
names. The species are tropical and 
subtropical. 

The whip scorpion, Mastigoproctus 
giganteas, occurs in southern Califor- 
nia, mainly in sandy desert places 
where it burrows in the sand under 
debris. They are commonly regarded 
as poisonous, although they cannot sting, but may bite. The writer 
has found that the natives invariably fear this creature very consider- 
ably, but knows of no evidence to justify this attitude. 




Fig. 225. — Whip scorpion (Pedipal 
pida) Mastigoproctus giganteus. X .8, 



VENOMOUS INSECTS AND ARACHNIDS 



373 



Solpugids 
Class Arachnida, Order Solpugida 

Characteristics of the Solpugida. — The solpugids are characterized 
in the Cambridge Natural History (Vol. IV, p. 423), viz. : " Tracheate 
Arachnids, with the last three segments of the cephalothorax free and 
the abdomen segmented. The chelicerse are largely developed and che- 
late, and the pedipalpi are leg-like, possessing terminal sense organs " 
(Fig. 226). 

The general appearance is spider-like ; they are very hairy, largely 
nocturnal, occurring in desert tropical regions. Though little is known 
about this interesting group, they are 
fairly common in certain portions of 
southern California, notably in the 
neighborhood of Salton Sea, where they 
are regarded as exceedingly venomous. 
The writer has been told that the pres- 
ence of one of the animals in a watering 
trough would result in the death of any 
animal drinking from the same. There 
is evidently not the slightest foundation 
for this belief. Their bite is benign. 
Common names applied to this order 
are "Sun Spider" and "Wind Scor- 
pion." 

The order is represented by a large 
number of species occurring only in 
tropical and subtropical countries, notably Africa. There are said to 
be only twelve species in the United States, all but one belonging to 
the two genera, Eremobates and Ammotrecha. 



,s^r^ 


Ss x 




E^ 


v ^Lq 




\x^4| 


1& 


A - \ 






kL— ' 



Fig. 226. — Sun spider (Solpugid), 
Eremobates cinerea. X 1. 



Centipedes 
Class Myriapoda, Order Chilopoda 

Characteristics of Myriapoda. — The Myriapoda are worm-like 
animals with separate head, possessing antenna?, and many fairly similar 
segments, each possessing one or two pairs of segmented appendages. 
Like the insects they are tracheated and for the most part terrestrial. 

The class Myriapoda is divided into four or five orders of which the 
following are well known, viz.: Chilopoda, the centipedes, with only 
one pair of appendages to each segment; and the Chilognatha 
(Diplopoda), the Millipedes, with two pairs of appendages to each 
segment, e.g. Julus nemorensis, a so-called " thousand-legged worm." 

Characteristics of Centipedes. — The Chilopoda have only one pair 
of appendages to each segment and are widely separated at the bases, 



374 MEDICAL AND VETERINARY ENTOMOLOGY 



the antennae are many jointed, the genital pore is located on the 
terminal body segment. The larger species, at least, are carnivorous, 
feeding mainly on insects. Notwithstanding the confusing abundance 
of walking appendages the centipedes crawl very rapidly. 

Unlike the Millipedes, which possess no organs of defense except 
glands which secrete an offensive odor, the Centipedes are provided 
with powerful poison claws located immediately ven- 
tral to the mouth, and connected by means of a hollow 
tube with large poison glands. 

The larger species of Centipedes belong to the 
following genera : viz., Scolopendra, Lithobius and 
Geophilus, and may be over six inches in length, 
some are reported to be eighteen inches long. 

Venomous Centipedes. — The larger centipedes 
are commonly regarded as very venomous, and it 
is said that their bite may be fatal to man. It is 
true that an insect captured by Scolopendra or 
Lithobius is killed almost instantly when the poison 
claws close upon it. 

In southern California the large greenish cen- 
tipede Scolopendra heros Girard (Fig. 227) is greatly 
feared. It measures from four to five inches in 
length and has a very formidable appearance. It 
is said that it not only punctures the skin with its 
poison claws, causing considerable pain, but also 
produces a " reddish streak where it has crawled 
upon the body." It is interesting to know that 
these animals are also markedly phosphorescent, which may possibly 
account for some of the phenomena produced on the skin. Geophilus 
electricus and G. phosphoreus are notable examples of phosphorescent 
species. 




Fig. 227. — A ven 
omous centipede 
Scolopendra 
X .66. 



APPENDIX I 
GENERAL CLASSIFICATION OF BACTERIA AND PROTOZOA 

Differences in Methods of Study in Bacteria and Protozoa. — The 

lowest forms of animal life belong to the Protozoa, while the lowest 
forms of vegetable life belong to the Bacteria in a broad sense. Since 
the epoch-making discoveries of Pasteur and Koch, advancing the 
"germ theory" of disease, these organisms have been the objects of 
research in many lands and by many investigators, and distinct sciences, 
namely, Bacteriology and Protozoology, have been developed. The 
methods of study in the two branches are rather different, inasmuch as 
Bacteria may be studied in culture media, while the Protozoa ordinarily 
require different methods, i.e. are not as readily amenable to culture 
media. Calkins has stated this in the following clear terms : " The 
study of protozoa, even when possible to apply bacteriological methods, 
is fundamentally different from the study of bacteria, as at present 
carried on. The latter, dependent on growth conditions, colony forma- 
tion, reactions to media, etc. are essentially physiological, and based 
upon the function of the organisms. The study of protozoa, on the 
other hand, is essentially morphological, or based upon the structures 
of the protozoan cell, and involves the changes in cell structures which 
an individual undergoes during various phases of vitality. Hence it 
becomes necessary first of all to know the life history of the protozoon, 
and the fundamental modification which its protoplasm assumes. " 
The student of Medical Entomology should not only be familiar with 
general structures and life history processes, but also with the methods 
of study applied in the laboratory such as the preparation and use of 
culture media, animal experimentation, etc. 

The Bacteria. — There are " only three principal types of bacteria, 
— the sphere, the rod and the spiral. Under normal and uniform condi- 
tions of life each breeds true, the spherical producing spheres and the 
rods, again, only rods." * 

Classification. — The following classification after Migula, 2 adapted 
after Jordan, with the addition of examples in the transmission of which 
insects and arachnids are concerned, will serve as a general guide in 
locating certain diseases touched upon in the preceding chapters. Un 
fortunately, contrary to the statements made above, it seems necessary 

1 Jordan, Edwin O., 1908. Textbook of general bacteriology, 557 pp. 
W. B. Saunders Co. 

2 Migula. System der Bacterien, Jena, 1897 (after Jordan, loc. cit.). 

375 



376 MEDICAL AND VETERINARY ENTOMOLOGY 

to resort to a classification based on structural, instead of physiological, 
characters (Fig. 228). 



A 



r** 



**~ 




C 

Fig. 228. — Illustrating types of bacteria. A. Sphere or coccus; B. Rod or bacillus; 
- C. Spiral or spirillum ; D. Example of higher bacteria. (Adapted in part after Jordan. 
Greatly enlarged.) 

I. Cells globose in a free state, not elongating in any direction before division 

into 1, 2 or 3 planes 1. Coccaceae 

II. Cells cylindrical, longer or shorter and only dividing in one plane, and 
elongating to about twice the normal length before the division. 

a. Cells straight, rod-shaped, without sheath, non-motile, or motile by means 

of flagella 2. Bacteriacese 

b. Cells crooked, without sheath 3. Spirillacese 

c. Cells inclosed in a sheath 4. Chlamydobacteriaceae 

1. Coccaceae 
Cells without organs of motion 

a. Division in one plane Streptococcus 

e.g. Streptococcus erysipelatis of erysipelas 

b. Division in two planes Micrococcus 

e.g. Micrococcus melitensis of malta fever 

c. Division in three planes Sarcina 

Cells with organs of motion 

a. Division in two planes Planococcus 

b. Divisions in three planes Planosarcina 

2. Bacteriacese 

Cells without organs of motion Bacterium 

Cells with organs of motion (flagella) 

a. Flagella distributed over the whole body . . . Bacillus 
e.g. Bacillus anthracis of anthrax 
Bacillus typhosus of typhoid 
Bacillus pestis of bubonic plague 
Bacillus tuberculosis of tuberculosis 



APPENDIX I 377 

b. Flagella polar Pseudomonas 

3. Spirillacese 
Cells rigid, not snake-like or flexuous 

a. Cells without organs of motion Spirosoma 

b. Cells with organs of motion (flagella) 

1. Cells with 1, very rarely 2 to 3 polar flagella . Microspira 

2. Cells with polar flagella-tufts Spirillum 

e.g. Spirillum (vibris) cholerce of Asiatic cholera 

Cells flexuous (see also under Protozoa) Spirochceta 

e.g. Spirochceta duttoni of African relapsing fever 

4. Chlamydobacteriacese (higher bacteria) 
Cell contents without granules of sulphur 

a. Cell threads unbranched. 

I. Cell division always only in one plane . . . Streptothrix 
II. Cell division in three planes previous to the formation of gonidia : 

1. Cells surrounded by a very delicate, scarcely visible sheath. 

(marine) Phragmidiothrix 

2. Sheath clearly visible (fresh water) .... Crenothrix 

b. Cell threads branched Cladothrix 

Cell contents containing sulphur granules Thiothrix 



The Protozoa 

Classification of the Protozoa. 1 

Phylum Protozoa ; Unicellular animals (Fig. 1) 

Subphylum Mastigophora. Flagella-bearing protozoa 
Class zoomastigophora. Undisputed animal flagellates 
Subclass Lissoflagellata without protoplasmic collars 

Order Spirochsetida 
e.g. Spirochceta duttoni of African relapsing fever, carried by a tick, 

Ornithodorus moubata 
e.g. Spirochceta gallinarum of poultry spirochetosis, carried by a tick, 

Argas persicus 
e.g. Treponema pallidum of Syphilis 

Order Trypanosomatida 
e.g. Trypanosoma gambiense of African sleeping sickness, carried by a 

Tsetse fly, Glossina palpalis 
e.g. Trypanosoma brucei of Nagana (disease of certain African beasts 

of burden), carried by a Tsetse fly, Glossina morsitans 
Subclass Choanoflagellata. With protoplasmic collar ■. 
(No pathogenic species) 
Class Phytomastigophora. With plant characteristics 
(No pathogenic species) 
Subphylum Sarcodina. Protozoa with pseudopodia only 
Class Rhizopoda. Pseudopodia without axial filaments 
Subclass Amcebsea. With firm lobose pseudopodia 

Order Gymnamcebia 
e.g. Entamceba histolytica of tropical dysentery 
Class Actinopoda. With supporting axial filaments 
(No pathogenic species) 
Subphylum Infusoria. Motile organs, cilia ; dimorphic nuclei 
Class Ciliata. Without tentacles ; always ciliated 
Order Holotrichida 

1 Adapted after Calkins, including only groups of pathogenic importance. 



378 MEDICAL AND VETERINARY ENTOMOLOGY 

e.g. Balantidium coli; causative organism of a type of dysentery known 

as Balantidiosis 
Class Suctoria. With suctorial tentacles ; embryos ciliated 
(No pathogenic species) 
Subphylum Sporozoa. No motile organs ; reproducing by spores 
Class Telosporidia. Reproduction ends life of cell 
Subclass Gregarinida. Lumen-dwelling sporozoa 

Order Schizogregarinida 
e.g. Ophryocystis 

Order Eugregarinida 
e.g. Monocystis 
Subclass Coccidiidia. Cell-dwelling sporozoa 

Order Tetrasporocystida 
e.g. Coccidium tenellum ( ?) of Blackhead in turkeys 
Subclass Hsemosporidia. Sporozoan parasites of the blood 

Order Hsemosporida 
e.g. Hcemamoeba (Proteosoma) relicta of bird malaria in sparrows; in 
India carried by Culicine mosquitoes 
Order Xenosporida 
e.g. Plasmodium vivax of tertian malaria, carried by certain Anopheline 

mosquitoes 
e.g. Babesia bigemina of Texas cattle fever, carried by a tick, Mar- 
gar opus annulatus 
e.g. Piroplasma hominis (doubtful or disproven) of Rocky Mountain 
spotted fever of human beings, carried by a tick, Dermacentor 
venustus 
Class Neosporidia. Reproduction with continued life of cell 
Subclass Myxosporidia. Spores with distinct capsules 

Order Myxosporida 
e.g. Myxobolus cyprini of pox disease of the carp 

Order Microsporida 
e.g. Nosema bombycis, causative organism of pebrine in silkworms 



INDEX 



Acanthiidse, 69, 353. 
Acariasis, 330. 

psoroptic, 337. 

sarcoptic, 330. 
Acarina, 296, 330. 
Acarus muscarum, 197. 
Achorion schoenleini, 62. 
Aculeate hymenoptera, 358. 
"Adobe" tick, 323. 
^Edes calopus, 3, 35, 88, 92, 114, 117. 
Mdes (genus), 100. 
^Edinae, 86, 97, 99. 
jEdini, 87. 
^Edomyia, 100. 
African coast fever, 313. 

relapsing fever, 327. 

relapsing fever tick, 326. 

relapsing fever tick control, 328. 

sleeping sickness, 8, 34, 210. 

sleeping sickness control, 213. 

sleeping sickness reservoirs, 212. 

sleeping sickness transmission, 212. 
Agramonte, 113. 
Aldrichia, 98. 
Alpine scurvy, 145. 
Amblycera, 53. 
Amblyomma americanum, 301, 316, 

321. 
Amblyomma (genus), 323. 
American roach, 39. 
Ammonia, for cone- nose bite, 79. 
Ammotrecha, 373. 
Amoebic dysentery, 8. 
Anarsia lineatella, 348. 
Anatomy, insect, 13. 

external, 19. 

internal, 14. 
Anderson, J. F., and Frost, W. H., 224. 
Andre, Charles, 181. 
Angoumois grain moth, 348. 
Ankylostoma caninum, 183. 
Ankylostoma duodenale, 8, 9. 
Annelida, 10. 
Anopheles (genus), 2, 5, 87, 88, 97, 98. 

aitkeni, 99. 

albimanus, 112. 

algeriensis, 98. 

arabiensis, 98. 

argyrotarsus, 112. 

barberi, 98. 

bifurcatus, 98. 

claviger, 104. 



control of, 120. 

corethroides, 98. 

crucians, 89, 98, 112. 

dthali, 98. 

eiseni, 98. 

franciscanus, 98. 

gigas, 98. 

immaculatus, 99. 

lindsayi, 99. 

maculipennis, 11, 98, 112. 

nigripes, 99. 

pseudopunctipennis, 98. 

punctipennis, 98, 112. 

quadrimaculatus, 112. 

smithi, 99. 

welcomei, 98. 

wing of, 81. 
Anopheline characteristics (see Mos- 
quitoes) 
Anophelini, 86, 88. 
Anthomyia radicum, 241, 242. 
Anthomyidae, 241, 263. 
Anthonomus grandis, 348. 
Anthrax, 34, 35, 46, 72, 145, 151. 
Anthrenus museorum, 46. 

scrophulariae, 46. 

verbasci, 46. 
Ant lion, 21. 

mouth parts of, 32. 
Ants, stinging, 358. 

velvet, 358. 
Apatolestes, 156. 
Aphaniptera, 273. 
Aphis lions, mouth parts of, 32. 
Apidae, 359. 

Apiomerus crassipes, 77. 
Apis mellifera, 353, 359. 

mouth parts of, 31. 

sting of, 353. 
Aptera, 16, 18, 19. 
Arachnida, 12, 296, 330. 
Arachnid venoms, 351. 
Aradidas, 69. 
Araneida, 359. 
Argas americanus, 323. 

brumpti, 326. 

cucumerinus, 326. 

miniatus, 323. 

reflexus, 326. 

vespertillionis, 326. 
Argas persicus, 3, 323, 365. 

control of, 326. 



379 



380 



INDEX 



Argas persicus, damage done, 325. 

description of, 323. 

life history of, 324. 

relation to spirochetosis, 325. 
Argasidae, 298. 
Armigeres, 99. 
Arribalzagia, 97. 
Arsenical dips for ticks, 309. 
Arthropoda, 10. 
Ascaris canis, 183. 

lumbricoides, 8. 
Asiatic cholera, 181. 
Assassin bugs, 75. 
Asturian leprosy, 145. 
Atoxyl, against fly larvae, 195. 
Attagenus pellio, 47. 
Auchmeromyia luteola, 239. 
Australian roach, 39. 
Avicularia calif ornicus, 364. 
Aviculariidae, 364. 

Babesia bigemina, 34, 305, 306. 

caballi, 320. 

canis, 320. 

ovis, 320. 
BaciUus anthracis, 34, 47, 72, 145, 151. 

dysenteriae, 179. 

icteroides, 114. 

pestis, 33, 278. 

prodigeosus, 174. 

pyocyaneus aureus, 41. 

tuberculosis, 33, 180. 

typhosus, 177. 
Bacot, A. W., 283. 
Bacteria, classification of, 375. 
Balantidium coli, 9. 
Balfour, A., 326. 
Banks, Nathan, 273, 317, 330. 
Bartonia bacillif oralis, 117. 

bodies, 117. 
Bass, C. C, 102, 110. 
Bats, in mosquito control, 132. 
Bedbugs, 7, 11, 69, 353. 

bites of, 72. 

China, 77. 

control of, 73. 

disease transmission by, 72. 

habits and life history of, 71. 

how distributed, 71. 

mouth parts of, 32. 

of bat, 70. 

of poultry, 70. 

of swallow, 70. 
Bees, 32. 
Bee sting, 353. 
Beetles, 22. 

blister, 49. 

carpet, 46. 

carrion, 46. 

grain, 48. 

larder, 46. 

May, 47. 

mouth parts of, 32. 



relation to disease, 46. 

rove, 45. 

scavenger, 45. 

sexton, 46. 
Benzine for bedbugs, 73. 

for body louse, 67. 
Bignami, A., 102. 
Bird lice, 52. 
Bironella, 98. 

Bishopp, C. F., 221, 228, 317, 318. 
Biting lice, 21, 52. 

classification of, 52. 

control of, 57. 

damage done, 53. 

habits and life history, 52. 

mouth parts of, 32. ♦ 

of angora goat, 54. 

of cat, 54. 

of cattle, 54. 

of deer, 55. 

of dog, 54, 65. 

of duck, 55, 57. 

of goat, 54. 

of goose, 55, 57. 

of guinea pig, 57. 

of hen, 55, 57. 

of horse, 54. 

of pigeon, 56. 

of swan, 56, 57. 

of turkey, 55. 
Black fly, 148. 
Blaizot, L., 64. 
Blatella germanica (see Croton bug), 

39. 
Blatta orientalis, 39. 

as carrier of filaria, 43. 
Blepharoplast, 209. 
Blister beetles, 49, 351, 352. 
Blow fly, 237. 
Bluebottle fly, 237. 
Blue ointment for pubic louse, 67. 
Blue, Rupert, 281. 
Bollinger, O., 152. 
Bombidae, 359. 
Book louse, 8, 21. 

mouth parts of, 32. 
Boophilus (genus), 323. 

australis, 308. 

bovis, 300, 307. 

decoloratus, 308. 
Borax, for cockroaches, 44. 

for fly larvae, 195. 

lotion, 67. 
Botflies, 7, 13, 246. 

of cattle (see Hypoderma lineata). 

of deer, 257. 

of horse (see Gastrophilus equi). 

of humans, 258. 

of rodents, 257. 

red- tailed, 250. 
Bothriocyrtus californicus, 364. 
Bouton, 31. 
Bovine scabies, 343. 



INDEX 



381 



Braehiomyia, 99. 

Braun, M., 6, 49, 332. 

Breakbone fever, 117. 

Breathing system, tracheal, 13. 

Brill's disease, 64. 

Bristletails, mouth parts of, 32. 

Brown-tail moth, 351. 

Bruce, D., 210. 

Brumpt, E., 65, 79. 

Buboes, 33, 278. 

Bubonic plague, 2, 33, 278. 

Buffalo gnats, 143, 147. 

bites of, 145. 

breeding habits, 144. 

classification of, 147. 

control of, 147. 

larvae of, 143. 

pupae of, 144. 

relation to disease, 145. 
Bugs, 22. 

Buhach (see Pyrethrum). 
Bumblebees, 359. 
Buthidae, 371. 
Butterflies, 22. 

mouth parts of, 31, 32. 

Caddis flies, 22. 

mouth parts of, 32. 
Caeca, gastric, 15. 
Calliphora erythrocephala, 237, 262. 

vomitoria, 237. 
Calmette, 351. 
Campodea, 16. 
Cantharidae, 352. 
Cantharidin, 49. 
Carassius auratus, 133. 
Carbolic acid for fly larvae, 195. 

for myiasis, 240. 
Carbon bisulphide for bots, 249. 

for squirrels, 287. 
Carbuncle, 152. 
Cardo, 25. 
Carlet, G., 355. 
Carrion's disease, 117. 
Carroll, James, 95, 113. 
Cassa, J. LeR. Y, 140. 
Cassia, oil of, 132. 
Castellani, A., 182, 210. 
Castor bean tick, 321. 
Caterpillars, 14. * 

Cattini, J., 181. 
CeUia, 97, 112. 

argyrotarsis, 112. 
Centipedes, 11, 373. 
Centrums carolinianus, 371. 
Cephenomyia, 257. 
Ceratitis capitata, 264. 
Ceratophyllus acutus, 269, 276, 283, 
284. 

fasciatus, 7, 65, 270, 276. 

londinensis, 277. 

niger, 276. 
Cestoda, 7, 9. 



Cetonia aurata, 48. 

Chactidae, 371. 

Chaetopoda, 10. 

Chagas, C, 79. 

Chagas disease 79. 

Chagasia, 98. 

Chandler, W. L., 365. 

Charbon, 152. 

Cheshire, F. R., 353. 

Chevril, R., 243. 

Chiggers, 345. 

Chigoe, 247, 248, 291. 

Chilognatha, 373. 

Chilopoda, 373. 

Chinese bedbug, 77, 353. 

Chin fly, 250. 

Chironomidae, 81. 

Chlorine, for chicken dip, 58. 

Chloronaphtholeum for lice, 68. 

for equine mange, 334. 

for fly larvae, 195. 

for mosquitoes, 126. 

for myiasis, 240. 

for sheep dip, 295. 

for sheep scab, 343. 
Cholera, Asiatic, 181. 

fly, 197. 
Chowning, W. M. (Wilson, L. B., and), 

315. 
Christya, 97. 

Christophers, S. R. (see Stephens). 
Chrysanthemum cinerariafolium, 197. 
Chrysomyia macellaria, 6, 13, 234, 263. 
Chrysops, 156. 
Chub, Sacramento, 133. 
Cicada, mouth 'parts of, 32. 

killer, 359. 
Cimex hemipterus, 70, 73. 

lectularius (see also Bedbug), 70, 73, 
279. 

macrocephalus, 70. 

pilosellus, 70. 

pipestrelli, 70. 

rotundatus, 70. 
Cimicidae, 69. 
Cinchona, 102. 
Citellus beecheyi, 283. 
CitroneUa, oil of, 4, 131. 
Classification of insects, 15. 
Clypeus, 25. 
Cnemidocoptes gallinae, 336. 

mutans, 335. 
Coast fever, African, 313. 
Coccidium oviforme, 9. 
Cockchafers, 47. 
Cockroach, control of, 44. 

disease transmission by, 40. 

distribution of, 39. 

habits and life history of, 37. 

mouth parts of, 32. 

species, 39. 
Ccenurus cerebralis, 256. 
Cole, L. J., 171. 



382 



INDEX 



Coleoptera, 22, 32. 

larvae of, 13. 
Columbaez midge, 149. 
Cominensalism, 6, 8. 
Compsomyia macellaria, 234. 
Comstock, J. H., 353, 359, 363, 371. 
Comstock, J. H. (Needham, J. G., and) 

17. 
Cone-noses, 11, 32, 75, 352. 

bites of, 77. 

control of, 79. 

life history of, 78. 

treatment for bite, 79. 
Congo floor maggot, 239. 
Conorhinus protractus, 11, 77, 353. 
life history of, 78. 

megistus, 79. 

sanguisuga, 76, 352. 
Conseil, F., 64. 
Copeman, S. M., 169. 
Copper sulphate, 125. 
Cordylobia anthropophaga, 238. 
Corethra, 81. 
Corethrinae, 81. 
Corrodentia, 8, 21, 32. 
Corrosive sublimate for cone-nose bites, 

79. 
Corsair, two-spotted, 77. 
Cotalpa lanigera, 48. 
Cotton-boll weevil, 348. 
Cotton, E. C, 303. 
"Cow killer," 359. 
Craneflies, 80. 
Crawford, J., 177. 
Crayfish, 10. 
Creolin, for fly larvae, 195. 

for head louse, 66. 

for hen flea, 293. 

for lice on animals, 68. 

for mange, 335. 

for myiasis, 240. 
Creophilus, 46. 
Cresyl, for mosquitoes, 132. 
Crickets, 19. 
Crop (of insect), 14. 
Croton bug, 39. 

as carrier of bacteria, 41. 

life history and habits, 39. 
Crustacea, 10, 11. 
Ctenocephalus canis, 6, 270, 275. 

felis, 275. 

musculi, 270, 274. 

serraticeps, 275. 
Ctenopsyllidae, 273, 274. 
Cucujidae, 48. 
Culex, characters, 84, 89, 99. 

fasciatus, 114. 

fatigans, 116. 

malaria?, 104. 

penicillaris, 104. 

pipiens, 104, 131. 

pungens, 83. 

quinquefasciatus, 116, 117. 



Culicidae (characteristics), 80. 

Culicinae, 97, 99. 

Culicini, 86. 

Culiseta incidens, 83, 88. 

Cuterebra cuniculi, 257. 

emasculator, 257. 
Cyanide fumigation, 74. 
Cyanide, sodium for fly larvae, 195. 
Cyclolepteron, 97. 
Cyprinodon dispar, 134. 
Cysticercus trichodectes, 65. 

Dacus oleae, 264. 

Damsel flies, mouth parts of, 32. 

Darling, G. T., 126. 

Datura stramonium, 132, 197. 

Davidson, A., 78. 

Deaderick, W. H., 107. 

Deinokerides, 99. 

Delphinium, 66, 67. 

Demodecidae, 344. 

Demodex folliculorum, 344. 

var. bovis, 345. 

var. canis, 345. 

var. hominis, 345. 

var. suis, 345. 
Dengue, 117. 
Depluming mites, 336. 
Dermacentor (characteristics), 322. 

electus, 303. 

marginatus, 316. 

occidentalis, 321, 365. 

reticulatus, 320. 

variabilis, 7, 316, 321, 365. 

venustus (see Tick of spotted fever), 
317. 
Dermanyssidae, 346. 
Dermanyssus gallinae, 3, 12, 347. 

control of, 347. 

damage done, 347. 

habits, 347. 
Dermatitis, 348. 
Dermatobia cyaniventris, 258. 

hominis (see Warble), 258. 

noxialis, 258. 
Dermestes lardarius, 46. 

vulpinus, 46. 
Dermestidae, 46. 
Dewevre, 62. 
Diachloris, 156. 
Diarrhea, summer, 179. 
Dibothriocephalus latus, 183. 
Digestive system of insects, 14. 
Dip, kerosene for horn fly, 231. 

hme and sulphur, 339. 

for bovine scabies, 343. 

for sheep scabies, 339. 

for swine mange, 332. 
Diplococcus pemphigi contagiosi, 62. 
Diplopoda, 373. 
Dipping for horn flies, 231. 

for ticks, 308. 
Dipping cattle, 343. 



INDEX 



383 



Dipping, sheep, 341. 

swine, 332. 
Diptera, 22. 

Dipteron type of mouth parts, 28, 32. 
Dipterous larvae, 13. 
Dipylidium caninum, 9, 65, 183. 
Disease, causation by insects, 35. 

transmission by insects, 34. 
Distomum americanum, 9. 
Dixidse, 82. 
Doane, R. W., 141. 
Dobson flies, 21. 

larvae of, 14. 

mouth parts of, 32. 
Docophorus cygni, 56 

icterod.es, 55. 
Dog tick, 303. 
Dragon flies, 21, 132. 

mouth parts of, 32. 
Drepanidotaenia infundibuliformis, 9. 
Drone fly, 244. 
Dumdum fever, 72. 
Dutton, J. E., 210. 

Dutton, J. E. (Todd, J. L., and), 327. 
Dysentery, 3, 179. 

amoebic, 9. 

Earthworms, 10. 
Earwigs, 19. 

mouth parts of, 32. 
Echidophaga gallinacea, 8, 274, 278, 

292. 
Echinorhychus gigas, 47. 
Economic losses due to certain insects, 3. 
Ectoparasites, 6. 
Elephantiasis, 115. 
Empusa muscae, 197. 
Entamoeba histolytica, 8, 179. 
Entoparasites, 6. 
Ephemerida, 21, 32. 
Epipharynx, 25. 
Equine mange, 333. 
Eretmapodites, 99. 
Eremobates, 373. 
Eristalis tenax, 244. 
Esten, W. M. (Mason, C. J., and), 42, 

175. 
Eucalyptus, 132. 
Euplexoptera, 19, 32. 
Euproctes chrysorrhea, 351. 
Euthrips pyri, 51. 

striatus, 51. 

tritici, 51. 
Eurypelma hentzii, 364. 
Evans, W. J., 210. 
External parasitism, 36. 

Facultative parasites, 6. 
Faichnie, M., 179. 
False gid, 255. 
Fannia canicularis, 241. 

in urinary tract, 243. 

scalaris, 241, 242. 



Fasciola hepatica, 9. 
Favus, 62. 

Felt, E. P., 45, 185, 285. 
Feltinella, 97. 
Ficker, M., 179. 
Filaria bancrofti, 115. 

rytipleuritis, 43. 

sanguinus hominis, 115. 
Filariasis, 115. 
Finlay, C, 113. 
Firth, R. H. (Horrocks, W. M., and), 

179. 
Fishberry, for pubic louse, 67. 
Fish in mosquito control, 132. 
Fleas, 6, 22, 32, 266, 353. 

characteristics of, 266. 

classification of, 273. 

control of, 284. 

hosts of, 270. 

life history of, 267. 

light reactions of, 273. 

longevity of, 270. 

mouth parts of, 32, 281. 

of cat, 275. 

of dog, 270, 275. 

of hen, 8, 278, 292. 

of human, 270, 275. 

of mouse, 270. 

of rat, 270, 276. 

of squirrel, 270, 276. 

plague transmission by, 282. 
Flesh flies, 233. 

adult characteristics, 233. 

larval characteristics, 233. 
Fletcher, J., 230. 
Flexner, S., 222. 
Flies, bot, 246. 

caddis, 22. 

dragon, 21. 

flesh, 233. 

forest, 293. 

gad, 149. 

horse, 149. 

house, 22, 160. 

May, 21. 

papatici, 82. 

scorpion, 22. 

stone, 21. 

warble, 251. 
Floor maggot, 239. 
Fly cholera, 197. 

fungus, 197. 

poisons, 196. 

traps, 192. 
Follicle mites, 344. 
Follicular mange, 344. 
Food ordinance, 205. 
Force, J. N., 204. 
Forest flies, 293. 
Formaldehyde, for flies, 196. 
Formic acid, 351. 
Formicidae, 358. 
Formicina, 358. 



384 



INDEX 



Fowl tick (see Argas persicus). 

Frambcesia, 181. 

Francis, M., 240. 

Frisbie, E. F., 353. 

Frost, W. H., 222. 

Frost, W. H. (Anderson, J. F., and), 224. 

Fuchs, C, 363. 

Fumigation, for bedbugs, 73. 

for lice, 68. 

with carbon bisulphide, 287. 

with hydrocyanic acid gas, 74. 

with sulphur, 75. 
Fundulus, 134. 

Gadflies, 149. 
Galea, 25. 
Galeb, O., 43. 
GaU flies, 22. 
Gamasidae, 346. 
Gamasoidea, 346. 
Gambusia amnis, 133. 
Gametes of malaria, 111. 
Gametocytes of malaria, 110. 
Garbage cans, 190. 

disposal, 191. 
Garmen, H., 146. 
Gasoline for bedbugs, 73. 

for body louse, 67. 
Gastric caeca, 15. 

myiasis, 243. 
Gastrophilus equi, 7, 246. 
life history of, 247. 
pathogenesis, 248. 
prevention, 249. 
treatment, 249. 

haemorrhoidalis, 249. 

nasalis, 250. 

pecuarum, 250. 
Geophilus electricus, 374. 

phosphoreus, 374. 
Gerlach, A. C, 332. 
Gid, 256. 

false, 256. 
Giles, G. M., 95. 
Giltner, H. A., 117. 
Gizzard (insect), 14. 
Glossina flies (see Tsetse flies). 

fusca, 212, 215. 

longipalpis, 215. 

longipennis, 215. 

morsitans, 211, 214. 

pallicera, 215. 

paUidipes, 215. 

palpalis, 211, 212, 214. 

var. wellmani, 212, 214. 
Gnats, buffalo (see Buffalo gnats), 143. 

black, 148. 

classification of, 147. 

control of, 147. 

columbacz, 149. 

turkey, 148. 
Goldberger, J. (Shamberg, J. F., and), 
349. 



Goldfish, in mosquito control, 133. 
Golgi, C, 102. 

cycle of, 108. 
Goniocotes abdominalis, 55. 

compar, 56. 

hologaster, 55. 
Goniodes damicornis, 56. 

stylifer, 55. 
Goniops, 156. 
Graells, F., 362. 
Grain beetles, saw-toothed, 48. 
Grampus, 372. 

Grasshopper, mouth parts, 25, 32. 
Grassi, B., 102, 104. 
GraybiU, H. W., 298, 302, 308. 
Greenbottle fly, 238. 
Ground squirrels, 283. 
Grub in the head, 255. 
Grubs, 13. 

Gunpowder, for roaches, 45. 
Gypsum, as an insecticide, 195. 
Gyropidae, 53. 

species of, 57. 
Gyropus gracilis, 57. 

ovalis, 57. 

Hadrurus hirsutus, 12, 371. 
Haemagogus, 100. 
Haemamceba malariae, 108. 

praecox, 106. 

vivax, 107. 
Haemaphysalis, 322. 

leachi, 320. 

leporis, 321. 

palustris, 321. 
Haematobia serrata (see Horn fly). 
Haematopinus acanthopus, 62. 

asini, 61. 

eurysternus, 61. 

hesperomydis, 62. 

macrocephalus, 61. 

pedalis, 61. 

piliferus, 61. 

spinulosis, 62, 65. 

suturalis, 62. 

suis, 61. 

vituli, 61. 
Haematopota, 156. 
Haematosiphon inodorus, 70. 
Halteres, 17. 
Harvest mites, 345. 

treatment for, 346. 
Haushalter, and Spillman, 180. 
Haustellata, 24. 

Head maggot of sheep, 255, 265. 
characteristics of, 255. 
life history of, 255. 
prevention of, 257. 
symptoms of, 256. 
treatment of, 257. 

of deer, 257. 
Heel fly, 251. 
Heim, F., 47. 



INDEX 



385 



Hellebore for fly larvae, 195. 
Helminthes, 7. 
Hemiptera, 7, 22, 69. 

heteroptera, 17, 69. 

homoptera, 17. 

parasita, 17. 

mouth parts of, 28, 32. 

wings of, 17. 
Heterandria formosa, 133. 
Heteropoda, 360. 
Hewitt, S. G., 160. 
Hill, J. H., 222. 
Hine, J. S., 156, 234. 
Hippobosca equina, 295. 
Hippoboscidae, 293. 
Hirudinea, 10. 
Hirudo medicinalis, 10. 
Histeridae, 46. 
Hodge, C. F., 166, 190. 
Homalomyia canicularis, 241. 
larva of, 263. 

scalaris, 241. 
larva of, 263. 
Homoptera, 69. 
Honeybee, 353. 

lateral appendages of, 355. 

morphology of, 354. 

operation of, 356. 

sting of, 353. 
in situ, 357. 

venom sac and glands, 355. 
Hookworm of man, 8, 9. 
Hooker, W. A., 328. 
Hoplopsyllus, 273. 

anomalus, 278, 283. 
Horn fly, 3, 228. 

characteristics of, 229. 

control of, 230. 

damage done, 230. 

larvae of, 262. 

life history of, 229. 
Horrocks, W. M. (Firth, R. H., 

179. 
Horseflies, 7, 149. 

autumn, 158. 

bites of, 151. 

black, 156. 

black and white, 157. 

breeding habits of, 149. 

classification of, 155. 

control of, 155. 

green-headed, 157. 

larvae of, 149. 

lined, 158. 

mouth parts of, 29, 32. 

relation to anthrax, 151. 

relation to surra, 152. 
Horvath, G., 69. 
House fly, 160. 

breeding habits, 163, 167. 

campaigns against, 198. 

carrier of helminth ova, 182. 

control of, 184. 



and) 



description of, 160. 

distribution of sexes, 161. 

economic considerations, 171. 

influence of temperature on, 166. 

larvae of, 262. 

longevity of, 169. 

mouth parts of, 31, 32. 

natural enemies of, 197. 

ordinances against, 199. 

range of flight, 169. 

relation to disease, 171. 

relation to light, 170. 
Howard, L. O., 3, 76, 78, 83, 94, 95, 
102, 131, 133, 155, 165, 171, 
179, 180, 182, 197, 201, 361. 
Howe, L., 182. 
Hunter, W. D., 317. 
Hyalomma, 323. 

Hydrocyanic acid gas fumigation, 74. 
Hymenolepis diminuta, 183. 

nana, 183. 
Hymenoptera, 22, 358. 

mouth parts of, 31, 32. 
Hypoderma lineata (see Warble fly). 

bovis, 252. 
Hypopharynx, 27. 
Hypopus, 349. 

Ichneumon flies, 22. 
Imago (stage), 19. 
Impetigo, 62. 
Infantile paralysis, 221. 
Infection, direct, 35. 

indirect, 35. 

septicaemic, 35. 
Infusoria, 9. 
Insect anatomy, 13. 

classification, 15. 

larvae, 13. 

venoms, 351. 

wings, 15. 
Insecta, 11. 

Insecticides on manure, 193. 
Insects, disease transmission by, 34. 

disease causation by, 35. 

venomous, 351, 352. 
Intermittent parasites, 7. 
Internal parasitism, 36. 
Intestinal myiasis, 243. 
Iodine, tincture of, for follicle mites, 

345. 
Iron sulphate against fly larvae, 195. 
Irrigation as affecting mosquito control, 

128. 
Ischnocera, 53. 

Ischnoptera pennsylvanica, 39. 
Isometrus macula tus, 371. 
Isoptera, 21, 32. 
Isosoma tritici, 348. 
Itch, 331. 

treatment of, 332. 

grocers', 349. 
Ixodes, 322. 



386 



INDEX 



Ixodes ricinus, 298, 301, 321, 365. 

var. calif ornicus, 321. 
Ixodoidea, 296, 298. 

Jackson, D. D., 178. 

Jail fever, 64. 

Jan thino soma, 99. 

Jepson, F. P. (Nuttall, G. H. F., and). 

182 
Jigger flea,' 274, 278, 291. 
Jiggers, 345. 
Jirnson weed, 132, 197. 
Joint- worm of wheat, 348. 
Jordan, E. O., 177, 180. 
Julus nemorensis, 373. 

Kala azar, 72. 
Kellogg, V. L., 39, 55. 
Kerosene, for body louse, 67. 

for bedbugs, 73. 

for fowl tick, 326. 

for head louse, 66. 

for manure, 194. 

for poultry mite, 347. 

for pubic louse, 67. 

for scaly leg, 336. 
Kerteszia, 98. 
Kilbourne, F. L., 305, 306. 
KiUifishes in mosquito control, 134. 
King, A. F. A., 102. 
Kissing bug, 76, 352. 
Kitasato, 279. 
Koch, R., 102, 327. 
Kreso for equine mange, 334. 

for lice, 68. 

for hen fleas, 293. 

for sheep dip, 295. 

for sheep scab, 343. 

Labrum-epipharynx, 25. 
Lachnosterna arcuata, 48. 

fusca, 48. 
Lacinia, 25. 
Lantz, D. E., 285. 
Larkspur, for head louse, 66. 

for lice, 68. 

for pubic louse, 67. 
Larvaecides, 126. 
Larvae, insect, 13. 
Larvicide, 126. 
Latrine fly, 242. 

larva of, 263. 
Latrodectes mactans, 12, 360. 
bite of, 361. 
life history of, 363. 

malmigniatus, 362. 
Laveran, A., 102. 
Lavender, oil of, 132. 
Laverania malaria?, 108. 
Lavinia exilicauda, 133. 
Law, James, 334. 
Lazear, J. W., 113. 
LeConte, J. L., 76. 



Leech, medicinal, 10. 

Legislation against mosquitoes, 137. 

Leidy, J., 177. 

Leishman, W. B., 328. 

Leishman donovan bodies, 73. 

Leishmania donovani, 73. 

Lepidoptera, 22. 

larvae of, 13. 

mouth parts of, 31. 
Leprosy, Asturian, 145. 
Leptus autumnalis, 345. 
Lesser house fly, 241. 

larva of, 263. 
Leuciocus crassicandra, 133. 
Lewis, J. R,, 210. 
Lice, 7, 36, 52. 

biting (see Biting lice). 

control of, 57, 66, 68. 

dissemination of, 65. 

sucking (see Sucking lice). 
Ligula, 27. 
Lime sulphur for bovine scabies, 343. 

chloride of, on manure, 195. 

for sheep dip, 295. 

for sheep scab, 339. 

for swine mange, 332. 
Liotheidae, 53. 

species of, 57. 
Lipeurus, baculus, 56. 

heterographus, 55. 

poly trapezius, 55. 

squalidus, 55. 

variabilis, 55. 
Lipoptena depressa, 
Liston, W. G., 279. 
Lithobia, 374. 
Liverfluke, of cattle, 

of sheep, 9. 
Locusts, 19. 

Lone star tick, 301, 316, 321. 
Long, J. D., 288. 
Lophoscelomvia, 97. 
Lord, F. T., 180. 
Louse, body, 60, 64. 

crab, 60. 

head, 59. 

pubic, 60. 
Louse flies, 293. 

of deer, 295. 

of horse, 295. 

of sheep, 294. 
Low, G. C. (Sambon, L.W.,and), 102, 

105. 
Lucilia caesar, 238. 
larvae of, 263. 

serricata, 238. 
larvae of, 263. 
Lumbricus terrestris, 10. 
Lycosa tarentula, 364. 
Lytta vesicatoria, 49, 351. 



295. 



9. 



MacCullum, W. G. 
MacMe, F. P., 63. 



104. 



INDEX 



387 



Macrogametes of malaria, 111. 
Macrogametocytes of malaria, 110. 
Maggots, 7, 13. 
Malaria, 101. 

aestivo-autumnal, 106. 

circumstantial evidence of spread, 
102. 

control organization, 134. 
cost of, 134. 
educational factor, 137. 
legislation, 137. 
ordinances, 139. 
results of, 140. 

cycle of Golgi, 108. 

cycle of Ross, 108. 

economic considerations, 2. 

experimental evidence of spread, 103. 

gametes of, 111. 

gametocytes of, 110. 

historical sketch of, 101. 

inheritance by mosquitoes, 111. 

in river towns, 129. 

macrogametes of, 111. 

macrogametocytes of, 110. 

merocyte of, 108. 

merozoite of, 110. 

microgamete of, 111. 

microgametocyte of, 110. 

parasites of, 105. 

parthenogenetic cycle of, 108, 110. 

quartan, 108. 

quotidian, 108. 

schizogonic cycle of, 108. 

sporogonic cycle of, 108. 

sporozoite of, 108. 

tertian, 107. 

time factor in, 136. 

with reference to temperature, 111. 
Malignant pustule, 152. 
Mallophaga, 7, 21, 32, 52. 
Malmignatte, 362. 
Malpighian tubules, 15. 
Mandibles, 25. 
Mandibulata, 24. 
Mange, 331. 

bovine, 334. 

canine, 335. 

equine, 333. 

follicular, 344. 

of camels, 335. 

of cats, 335. 

of goats, 335. 

of swine, 332. 

treatment of, 332, 334, 335. 
Manson, Sir Patrick, 102, 105, 111, 115, 

116, 240, 278. 
Manson, P. Thurburn, 102, 105. 
Manure bins, 189. 

disposal, 187. 

insecticides for, 193. 

ordinances, 199, 204. 
Marchoux, E., 326. 
Marchoux, E. (Simond, P. L., and), 115. 

2c 



Marett, P. J., 119. 

Margaropus annulatus, 3, 12, 34, 297, 
300, 307. 

control of, 308. 

description of, 300. 

economic importance of, 301. 

life history of, 301. 

relation to Texas fever, 306. 
Marlatt, C. L., 71. 
Mason, C. J. (Esten, W. M., and), 42, 

175. 
Mastigoproctus giganteus, 372. 
May beetles, 47. 
May flies, 21. 

mouth parts of, 32. 
Mayo, N. S., 332. 
Maxillae, 25. 
McCoy, G. W., 283. 
Mease, James, 305. 
Mecoptera, 22, 32. 
Mediterranean fruit fly, 264. 
Megarhininae, 95, 99. 
Melanolestes abdominalis, 77. 

picipes, 77. 
Meloidae, 49, 351, 352. 
Melolontha melolontha, 48. 

vulgaris, 48. 
Melophagus ovinus (see Sheep tick). 
Menopon biseriatum, 8, 57. 

pallidum, 8, 57. 

titan, 8. 
Mentum, 25. 
Mercurial ointment for pubic louse, 

67. 
Mercurialis, 177. 
Merocyte of malaria, 108. 
Merozoite of malaria, 110. 
Messmates, 8. 
Metamorphosis, 18. 

complex or complete, 18. 

incomplete or simple, 18. 

primitive, 18. 

simple or incomplete, 18. 
Microfilaria bancrofti, 115. 

development of, 116. 
Microgamete of malaria, 111. 
Microgametocyte of malaria, 111. 
Midges, 81. 

columbacz, 149. 

Dixa, 82. 

owl, 118. 
Miller, 259. 

Millions, Barbadoes, 133. 
Millipedes, 11, 374. 

Minchin, E. A. (Thompson, D., and), 65. 
Minnows, top, 133. 
Mitchell, Evelyn, 100. 
Mitchell, J. D., 231. 
Mites, characteristics of, 330. 

depluming, 336. 

flour and meal, 349. 

follicle, 344. 

harvest, 345. ' 



388 



INDEX 



Mites, in ears of rabbits, etc., 344. 
itch, 331. 

life history of, 331. 
louse-like, 348. 
mange, 331. 
poultry, 3, 12, 346. 
psoroptic, 337. 
sarcoptic, 330. 
scab, 337, 339. 
scaly leg, 335. 
sheep scab, 12, 339. 
web-spinning, 350. 
Mitzmain, M. B., 153, 218, 221, 267, 

269. 
Moore, SirW., 177. 
Mosquito control organization, 134. 
cost of, 134. 
educational factor, 137. 
legislation, 137. 
ordinances, 139. 
results of, 140. 
time to begin, 136. 
Mosquitoes, 80. 
Anopheline, 33, 88. 

adults, 88. 

duration of life, 91. 

eggs, 88. 

flight, 92. 

hibernation, 92. 

larvae, 89. 

life history, 90. 

pupae, 90. 
bites of, 132. 
breeding places, 120. 
characteristics, 80, 86. 
control of, 120. 
fumigants for, 132. 
internal anatomy of, 84. 
life history of, 82. 
natural enemies of, 132. 
repellents, 131, 132. 
role in filariasis, 116. 
salt marsh, 130. 
sexual differences, 86. 
Yellow fever, 92. 

adults, 92. 

eggs, 94. 

larvae, 95. 

life history, 95. 

pupae, 95. 
Mosquito hawks, 132. 
Moths, 22. 

Mouth parts, classification, 24, 32. 
aphis lions, 32. 
ant lions, 32. 
ants, 32. 
bedbugs, 32. 
beetles, 32. 
book lice, 32. 
bristletails, 32. 
butterflies, 32. 
cicadas, 32. 
cockroaches, 32. 



cone-noses, 32. 

damsel flies, 32. 

dipteron type, 28, 32. 

dobson flies, 32. 

dragon flies, 32. 

earwigs, 32. 

fleas, 32. 

general, 23, 28. 

grasshoppers, 32. 

hemipteron type, 28, 32. 

honeybee, 31, 32. 

horseflv, 29, 32. 

house fly, 31, 32. 

hymenopteron type, 31, 32. 

lepidopteron type, 31, 32. 

May flies, 32. 

mosquitoes, 28, 32. 

moths, 32. 

orthopteron type, 24, 32. 

physopodan, 24, 27, 32. 

scorpion flies, 32. 

siphonaptera, 32. 

springtails, 32. 

stable fly, 30, 32. 

stone flies, 32. 

termites, 32. 

thrips, 27, 32. 
Multiceps multiceps, 256. 
Murray, Andrew, 59. 
Mus alexandrinus, 285. 

norvegicus, 285. 

rattus, 285. 
Musca domestica (see House fly). 
Muscidae, 160. 

characteristics of, 160. 
Muscidus, 99. 
Muscina stabulans. 262. 
Mutilhdae, 358. 
Mygale hentzii, 364. 
Myiasis, 233. 

gastric, 243, 245. 

identification of larvae in. 259. 

intestinal, 13, 243. 

treatment of, 240. 
Myriapoda, 11, 373. 
Myzomyia, 112. 

minimus, 112. 
Myzorhinchella, 97. 
Myzorhynchus, 97, 112. 

sinensis, 112. 

Nagana, 152, 213. 

Naphthaline flakes, 57. 

Nasonia brevicornis, 198. 

Necator americanus, 183. 

Necrophorus, 46. 

Needham, J. G. (Comstock, H. J., and), 

17. 
Nemathelminthes, 8. 
Neocellia, 98. 
Neopsylla, 274. 
Nettling hairs, 351. 
Neuroptera, 21, 32. 



INDEX 



389 



Neuropterous larvae, 13. 

Newman, S. W., 366. 

Newstead, R., 195. 

Nicofume, 126. 

NicoU, Wm., 182. 

Nicolle, C. N., 64. 

Nicotine for mosquitoes, 125. 

for sheep dip, 341. 
" Xo-see-ums, " 82. 
Nott, J. C, 113. 

Xuttall, G. H. F., 47, 60, 62, 72, 102, 
105, 113, 152, 177, 180, 212, 
279, 298, 326, 365. 
Nuttallia equi, 320. 
Nyssorhynchus, 97, 112. 

fuliginosus, 112. 

Obligatory parasites, 7. 
Odonata, 21, 32, 132. 
(Eciacus, 70. 

herundinus, 70. 

vicarius, 70. 
(Estridae, 13, 246, 264. 
(Estrus ovis, 255. 

larva of, 265. 
Oiling methods for mosquitoes, 122. 
Olive fly larva, 264. 
Ontological evidence, 13. 
Ookinete, 111. 
Oothecum, of roach, 37. 
Ophthalmia, 182. 
Opsicoetes personatus, 76, 352. 
Ordinances, fly, 199. 

food, 205. 

manure, 199, 204. 

mosquito, 139. 

stable, 199, 201. 
Oriental roach, 39. 
Ornithobius bucephalus, 57. 
Ornithodorus coriaceus, 298, 329, 365. 

damage done, 329. 

megnini, 328. 

moubata, 327, 370. 

savignyi, 329. 

treatment for, 329. 
Oroya fever, 117. 
Orthoptera, 19, 32. 

mouth parts of, 25. 
Osborn, H., 55, 236, 246, 255. 
Otacariasis, 344. 
Otitis, 344. 

Otodectes cygnotis, 344. 
Ovine scabies, 338. 

symptoms, 338. 

treatment, 339. 
Ox warble (see Warble fly). 
Oxyuris vermicularis, 183. 

Packard, A. S., 165. 

Packard, A. S. (Howard, L. 0., and), 361. 

Pajaroello tick, 329, 365. 

experiments with, 366. 

life history of, 369. 



Palpus, 25. 
Pangonia, 156. 
Panoplites, 99. 
Papatici fever, 119. 

flies, 82. 
Paraplasma flavigenum, 114 
Parasimulium, 147. 
Parasita, 58, 69. 
Parasitism, 6. 

degrees of, 8. 

external, 36. 

internal, 36. 
Paris green, 195. 

Parthenogenetic cycle of malaria, 110. 
Pasture rotation, 311. 
Pathogenic organisms, environment of, 

33. 
Patten, W. S., 73. 
Peach twig borer, 348. 
Pediculidae, 58. 
Pediculoides, 330. 

ventricosus, 348. 
Pediculosis, 58, 62. 
Pediculus capitis, 59. 

vestimenti, 60, 64. 
Pedipalpida, 372. 
Pelican, 8. 
Pellagra, 145. 

Pelopceus cementarius, 359. 
Pemphigus contagiosus, 62. 
Pennyroyal, oil of, 132. 
Peripatus, 11. 
Periplaneta americana, 39. 

australasia, 39. 
Pfeifler, R„ 102. 
Phenol, for head louse, 67. 
Philopterida?, 53. 

species of, 55. 
Phlebotomus, 82, 118. 
Phlebotomus papatasii, 119. 

verrucarum, 118. 
Phleothrips nigra, 51. 

verbasci, 51. 
Phorbia brassicas, 243. 
Phormia regina, 238. 
Phthiriasis, 58, 62. 
Phthirius inguinahs, 61. 
Physopoda, 22, 32, 50. 

mouth parts of, 27. 
Pike, Sacramento, 133. 
Piper, S. E., 289. 
Piroplasmia bigemina, 305, 306. 

hominis, 314. . 
Piroplasmosis, 305. 
Plague, 33, 278. 

transmission of, 278. 

by squirrels, 283. 

Plasmodium, 33, 35, 105. 

detection of, 105. 

falciparum, 106. 

falciparum quotidianum, 108. 

life history of, 108. 

malarias, 108. 



390 



INDEX 



Plasmodium praecox, 106, 110. 

vivax, 8, 107, 110. 
Plaster of paris, against roaches, 44. 
Platyhelminthes, 8. 
Plecoptera, 21, 32. 
Plotz, Harry, 65. 
Pogonomyrmex, 358. 
Poliomyelitis, 221. 
Polistes pallipes, 359. 
Polybia flavitarsis, 359. 
Pontia rapae, mouth parts, 31. 
Porchinski, I., 155. 
Potassium dichromate, 195. 
Poultry lice, control of, 57. 

mite (see Dermanyssus gallinae). 
Predaceous, 6. 
Privy, sanitary, 192. 
Prosimulium, 147. 
Proteosoma, 104. 
Protozoa, classification of, 377. 
Protracheata, 11. 
Proust, A., 47. 
Proventriculus, 14. 
Pruritis, 62. 
Psocidae, 8. 
Psorophora, 99. 
Psoroptes communis var. bovis, 343. 

var. equi, 344. 

var. ovis, 12, 330, 337, 338. 
Psoroptic acariasis, 330. 
Psychodidas, 82, 118. 
Ptinus, 47. 

Ptychocheilus grandis, 133. 
Pulex, 274. 

irritans (see Fleas), 8, 270, 275. 
Pulicidae, 273. 
Punkies, 82. 

Pyrethrum powder, 57, 197. 
Pyretophorus, 97. 
Pyrofume, 132. 
Pyroligneous acid, 195. 
Pyrosoma bigemina, 306. 

Quotidian malaria, 108. 

Rabbit bot, 257. 
Ransom, B. H., 3. 
Rasahus biguttatus, 77, 353. 

var. thoracicus, 78. 
Rat control, 285. 
Rat, filaria of, 43. 

fleas of, 2, 270, 276, 277. 
Rat-tailed larva, 244. 
Red bugs, 345. 
Red-tailed bot, 250. 
Reduviidae, 75, 352. 
Reduvius personatus, 76, 352. 
Reed, Walter, 95, 113. 
Relapsing fever, 63, 73. 
Repellents, mosquito, 131. 
Repp, John J., 347. 
Rhicephalus, 323. 

appendiculatus, 314. 



bursa, 320. 

capensis, 314. 

eversti, 314, 320. 

nitens, 314. 

sanguineus, 320, 321. 

simus, 314. 
Rhipicentor, 322. 
Richardson, M. W., 222. 
Ricketts, H. T., 64, 315. 
Ricketts, H. T. (Wilder, R. N., and), 64. 
Roach (a fish), 133. 

American, 39. 

Australian, 39. 

control, 44. 

disease transmission by, 40. 

Oriental, 39. 

Pennsylvanian, 39. 

poison, 44. 
Robertson, W., 313. 
Root maggot fly, 242. 
Rosenau, M. J., 223. 
Ross, R., 102, 105, 108, 110. 

cycle of, 108. 
Roundworms of man, 8. 
Rove beetles, 45. 
Rucker, W. C, 286. 

Sabethes, 100. 
Salivary reservoirs, 15. 
system of insects, 15. 
Salmon, D. E„ 305, 307. 
Salt marsh mosquitoes, 130. 
Sambon, L. W., 145, 146. 
Sambon, L. W. (Low, G. C, and), 102, 

105. 
Sand flea, 274, 291. 
Sarcophaga sarraceniae, 238. 
Sarcophagidae (see Flesh flies). 
Sarcopsylla, 274. 

penetrans, 278, 291. 
Sarcopsyllidae, 273, 274. 
Sarcoptes minor var. felis, 335 

mutans, 335. 
Sarcoptes scabiei, 331. 
var. cameli, 335. 
var. canis, 335. 
var. caprae, 335. 
var. equi, 331, 333. 
var. hominis, 331, 332. 
var. suis, 330, 331, 332. 
Sarcoptic acariasis, 330. 
Sarcoptidae, 330, 337. 
Saw-toothed grain beetle, 48. 
Sawyer, W. A., 224, 366. 
Scabies, 337. 
bovine, 343. 
equine, 344. 
ovine, 338. 
treatment, 343, 344. 
Scaly leg of fowls, 335. 

treatment, 336. 
Scarabaeidae, 47. 
Scavenger beetles, 45. 



INDEX 



391 



Scavenger flies (see Flesh flies). 
Schizogonic cycle of malaria, 108. 
Schizotrypanum cruzi, 79. 
Schmidt, C. L. A., 203. 
Schuffner's dots, 107. 
Sclerostomum equinum, 183. 
Scolopendra heros, 374. 
Scorpionida, 370. 
Scorpion flies, 22, 32. 
Scorpionidae, 371. 
Scorpions, 12, 370. 

classification, 371. 

characteristics, 370. 

sting of, 371. 

whip, 372. 

wind, 373. 
Screening for mosquitoes, 131. 
Screw worm fly, 3, 6, 234. 

as affecting animals, 237. 

as affecting man, 235. 

life history of, 234. 
Scurvy, Alpine, 145. 
Seal, W. P., 133. 
Seidelin, H., 114. 
Septicemic infection, 35. 
Shamberg, J. F. (Goldberger, J., and), 

349. 
Sheep louse fly, 294. 

maggot fly, 238. 
Sheep scab (see Ovine scabies). 

tick, 294. 

life history of, 294. 
pathogenesis, 294. 
Shiner, 133. 

Signet ring in malaria, 108. 
Silpha, 46. 
Silphidae, 46. 
Silvius, 156. 
Simmonds, M., 181. 
Simond, P. L., 279. 

Simond, P. L. (Marchoux, E., and), 115. 
Simpson, F., 287. 
Simuliidae (see Buffalo gnats). 
Simulium columbaczense, 149. 

meridionale, 148. 

occidentale, 148. 

pecuarum, 147. 

venustum, 148. 
Siphonaptera (see Fleas), 22, 32, 353. 
Sitotroga cerealella, 348. 
Sleeping sickness, African, 8, 34, 35, 210. 

control of, 213. 

reservoirs, 212. 

transmission of, 212. 
Smith, J. B., 71, 89, 132. 

Theobald, 305, 306. 
Snodgrass, R. E., 355. 
Sodium cyanide for fly larvae, 195. 
SoUman, T., 50. 
Solpugidae, 373. 
Sowbug, 10, 11. 
Spanish fly, 49. 
Sphaer ophthalmia occidentalis, 358. 



Sphecina, 359. 
Sphecius speciosus, 359. 
Spiders, 359. 

bird, 364. 

black widow, 360. 

hour glass, 360. 

red, 350. 

sun, 373. 

trap-door, 364. 
Spillman and Haushalter, 180. 
Spinose ear tick, 328. 
Spirillum choleras, 181. 
Spirochaeta carteri, 63. 

duttoni, 63, 73, 327. 

gallinarum, 325. 

marchouxi, 325. 

novyi, 63. 

pertenuis, 181. 

recurrentis, 63, 73. 
Spirochaetosis, 62, 63, 73. 

fowl, 325. 
Sporogonic cycle of malaria, 108. 
Sporozoa, 9. 

Sporozoite of malaria, 108, 111. 
Spotted fever, 314. 

symptoms of, 314. 

tick transmission of, 315. 
Sprays as repellents, 231. 
Spring tails, 32. 
Squirrel flea, 269, 276, 283. 
Squirrels as disseminators of plague, 
283. 

control, 287. 

ground, 283. 

poison, 289. 
Stable construction, 185. 

ordinance, 201. 
Stable fly, 215. 

as a cattle pest, 221. 

breeding habits, 216. 

characteristics, 215. 

control of, 228. 

habits, 216. 

in relation to infantile paralysis, 221 . 
poliomyelitis, 221. 
surra, 221. 

larva of, 262. 

light reactions of, 216. 

longevity of, 219. 

mouth parts of, 24, 30, 32. 
Staggers, 255. 
Staphylinidae, 45. 
Staphylinus, 46. 
Staphylococcus aureus, 174. 
Stegomyia, 5, 35, 87, 92. 

calopus, 88, 114. 
Stephens, J. W. W. (Christophers, S. 
R., and), 87, 88, 95, 107, 110, 208 , 
213. 
Sternberg,*G. M., 113. 
Stethomyia, 97. 
Stick tight flea, 292. 
Stiles, C. W., 183, 192, 259. 



392 



INDEX 



Sting (see Honeybee sting). 

of scorpion, 371. 
Stinging insects, 357. 
Stipes, 25. 
Stomoxys calcitrans (see Stable flv). 

glauca, 228. 

inornata, 228. 

nigra, 228. 
Stone flies, 31, 32. 
Submentum, 25. 
Sucking lice, 58. 

in relation to disease, 62. 

life historv of, 58. 

of dog, 61. 

of field mouse, 62. 

of ground squirrel, 62. 

of hog, 61. 

of horse, 61. 

of ox, 61. 

of rat, 62. 

of sheep, 61. 

of white footed mouse, 62. 
Sulphur, for body louse, 67. 

for roaches, 44. 

fumigation, 75. 
Summer diarrhea, 179. 
Sun disease, 145. 
Sun spider, 373. 
Surra, 152. 
Swingle, L. D., 294. 
Sydenham, T., 177. 
Sylvanus surinamensis, 48. 
Symbiotes auricularum, 344. 
Syphilis, 63. 
Syrphidae, 244. 

Tabanidae, 7, 34, 149, 155. 
Tabanus atratus, 156. 

costalis, 157. 

dorsovittata, 212. 

lineola, 158. 

mouth parts of, 29. 

punctifer, 157. 

striatus, 153, 158. 

stygius, 157. 
wing of, 16. 
Taenia cucumerina, 65. 

expansa, 19. 

serrata, 183. 

solium, 9, 183. 

marginata, 183. 
Taeniorhynchus, 99. 
Tapeworm of cattle, 9. 

of dog, 9, 65. 

of man, 9. 

of poultry, 9. 
Tarantulas, 360, 364. 
Tarantism, 364. 
Tarbardillo, 64. 
Tarsonemidae, 348. 
Termites, 21. 
Tetranychidae, 350. 
Texas fever, 3, 34, 305. 



Texas fly (see Horn fly). 

screw worm (see Screw worm fly). 
Theileria parva, 313. 
Thelyphonidae, 372. 
Theobald, F. V., 94, 95. 
Theobaldia incidens, 88. 
Thompson, D. (Minchin, E. A., and), 

65. 
Thornheaded worm, 47. 
Thousand-legged worm, 373. 
Thrips, 22, 27, 50. 

clover, 51. 

grass, 51. 

mullein, 51. 

pear, 51. 
Thysanoptera, 22, 27, 50. 
Thysanura, 16, 18, 32. 
Ticks, 296. 

adobe, 323. 

argasine, 323. 

bite remedies, 370. 

"castor bean," 321. 

classification of, 298, 321. 

deer, 321. 

dog, 303, 321. 

feeding habits of, 297. 

fowl (see Argas persicus). 

Ixodine, 300, 321. 

life history of, 297. 

"hmte star," 321. 

longevity of, 298. 

mouth parts of, 297. 

Pajaroello, 329, 365. 

paralysis caused by, 320. 

rabbit, 321. 

relapsing fever, 326. 

sheep, 294. 

spinose ear (see Ornithodorus 
megnini). 

spotted fever, 317. 
control of, 319. 
description of, 317. 
distribution of, 318. 
life history of, 317. 
longevity of, 318. 

tampan, 323. 

Texas fever, 3, 12, 300. 

venomous, 364. 

wood, 303, 321. 
Tipulidae, 80, 81. 
Tizzoni, G., 181. 
"Tlalsahuate," 345. 
Tobacco decoction for lice, 68. 

for mosquitoes, 125. 

dip for sheep scab, 341. 

dust bath, 57. 
Todd, J. L., 327. 
Torti, 102. 

Townsend, C. H. T., 118, 119 
Toxascaris limbata, 183. 
Toxorhynchites, 99. 
Tracheal breathing system, 13. 
Transitory parasites, 7. 



INDEX 



393 



Trematoda, 7, 9. 
Treponema pallidum, 63. 
Triatoma megistus, 79. 
Trichinella spiralis. 8. 
Trichinosis, 8. 

Trichocephalus trichiurus. 183. 
Trichodectes climax, 54. 

hermsi, 54. 

latus, 54, 65. 

parumpilosus, 54. 

scalaris, 54. 

subrostratus, 54. 

tibialis, 55. 
Trichodectidae, 53. 

species of, 54. 
Trichoprosopon, 99. 
Trichoptera, 22, 32. 
Trichuris trichiurus, 183. 
Trinoton lituratum, 57. 

luridum, 57. 
Troctes divinatoria, 8. 
Trombidiidse, 345. 

life history of, 345. 
Trombidium holoserieeum, 345. 

magnificum, 345. 
Trypanosoma brucei. 213. 

castellani, 210. 

evansi, 152, 221. 

gambiense, 8, 9, 34. 210. 

lewisi, 209. 

rhodesiense, 211. 

ugandense, 210. 
Trypanosomiasis. 208. 

Brazilian, 79. 

rat, 65. 
Trypetidae, 264. 
Tsetse flies, 207. 

characteristics of, 207. 

classification of, 214. 

habits of, 207. 

life history of, 208. 

relation to disease, 208. 
Tuberculosis, 33, 177. 
Tumbu flv, 238. 
Turkey gnat, 148. 
Turpentine for bots, 249. 
Two-spotted corsair. 77, 353. 
Tyroglyphus farina? . 349. 

siro, 349. 
Typhlopsylla, 274. 
Typhoid fever, 177. 
Typhus fever, 36, 64. 
Tyroglyphidae. 349. 
Tyzzer, E. E.. 352. 

Ulcer, tropical, 181. 
Uranotaenia, 100. 
Uropodidae, 346. 

Van Duzee, E. P.. 77. 
Vejovidae, 371. 



Vejovis carolinus, 371. 

Velvet ants, 358. 

Venomous insects and arachnids, 351. 

Venoms, haemolytic, 351. 

hsemorrhagic, 351. 

how introduced, 351. 

insect, 36, 351. 

neurotoxic, 351. 

scorpion, 351. 

spider, 360. 

tick, 364. 
Verjbitsky, A. T., 279. 
Verrucca peruana, 117. 
Verruga, 117. 

mode of transmission, 118. 
Vespa maculata, 359. 
Vinegerone, 372. 

Warble fly (see Warbles). 
Warbles, ox, 3, 13, 251. 

characteristics of, 251. 

economic losses due to, 253. 

in humans, 258, 264. 

injury done by, 252. 

life history of, 251. 

prevention of, 254. 

treatment for, 254. 
Warburton, C, 60. 
War fever, 64. 
Warren, George, 102, 105. 
Washburn, F. L., 249. 
Webster, F. M., 349. 
Wellman, F. C, 328, 370. 
Whip scorpions, 372. 
White ants, mouth parts of, 32. 
Wilder, R. N. (Ricketts, H. T.. and), 

64. 
WiUiston, S. W., 81, 160, 246, 293. 
Wilson, L. B., 315. 
Wind scorpions, 373. 
Wing of tabanus, 16. 
Wings of insects, 15. 
Wool sorter's disease, 152. 
Wyeomyia, 100. 

XenopsyUa, 274. 

cheopis, 270, 277, 279. 
Xestopsylla gallinacea, 292. 

Yaws, 181. 

Yellow fever, 3, 5, 113. 

commission, 113. 

etiology of, 114. 

mosquito carrier, 113. 
Yersin, 279. 

Zenoleum for depluming mites, 336. 
for hen flea, 293. 
for sheep scab, 343. 
for sheep tick, 295. 



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